title: Pfizer

text: On January 5, 2021, Pfizer introduced a new logo. In April 2021, Pfizer acquired Amplyx Pharmaceuticals and its anti-fungal compound fosmanogepix (APX001). In August, the company announced it would acquire Trillium Therapeutics Inc and its immuno-oncology portfolio for $2.3 billion ($18.50 per share). In December, Pfizer announced that it had agreed to acquire Arena Pharmaceuticals for $6.7 billion in cash. In March 2022, it was announced the acquisition of Arena Pharmaceuticals had been concluded. In April 2022, the company announced it would acquire ReViral Ltd, for up to $525 million, gaining access to experimental drugs used to combat respiratory syncytial virus infections. Pfizer completed the acquisition of ReViral in June 2022.


title: Pfizer

text: In October 2022, the company completed the acquisition of Biohaven Pharma and its calcitonin gene-related peptide programs for $11.6 billion. In August 2022, the company announced it would buy Global Blood Therapeutics for $5.4 billion, boosting Pfizer's rare disease business and helping with its aim to add $25 billion in revenue by 2030.


title: Pfizer

text: Pfizer has developed and launched several products in response to the COVID-19 pandemic, including the Pfizer–BioNTech COVID-19 vaccine and Paxlovid.


title: Pfizer

text: In March 2020, Pfizer joined the COVID-19 Therapeutics Accelerator funding vehicle to expedite development of treatments against COVID-19. The $125 million initiative was launched by the Bill & Melinda Gates Foundation in partnership with Mastercard and Wellcome Trust, with additional funding announced shortly after from Chan Zuckerberg Initiative, UK Foreign, Commonwealth and Development Office and Madonna.


title: Pfizer

text: The following month, the Foundation for the National Institutes of Health announced the Accelerating COVID-19 Therapeutic Interventions and Vaccines (ACTIV) public-private partnership to develop a coordinated research strategy for prioritizing and speeding up development of COVID-19 vaccines and pharmaceutical products. Pfizer joined the partnership as an industry "leadership organization", and participated as a collaborator in ACTIV-led clinical trials. CEO Albert Bourla attended the GAVI COVAX AMC 2021 Investment Opportunity Launch Event, otherwise named One World Protected, on April 15, 2021.


title: Pfizer

text: In Canada, Pfizer endorsed the use of a vaccine passport mobile app developed by CANImmunize in order to record and track status of COVID-19 vaccination.


title: Pfizer

text: As the scale of the COVID-19 pandemic became apparent, Pfizer partnered with BioNTech to study and develop COVID-19 mRNA vaccine candidates. Unlike many of its competitors, Pfizer took no initial research funds from the United States' Operation Warp Speed vaccine development program, instead choosing to invest roughly $2 billion of its own funds. Pfizer CEO Albert Bourla has said that he declined money from Operation Warp Speed to avoid government intervention, stating later that "when you get money from someone that always comes with strings. They want to see how we are going to progress, what type of moves you are going to do. They want reports. And also, I wanted to keep Pfizer out of politics, by the way."


title: Pfizer

text: In May 2020, Pfizer began testing four different COVID-19 vaccine variations using lipid nanoparticle technology provided by Canadian biotechnology company Acuitas Therapeutics. Vaccines were injected into the first human participants in the U.S. in early May. In July 2020, Pfizer and BioNTech announced that two of the partners' four mRNA vaccine candidates had won fast track designation from the FDA. The company began PhaseII-III testing on 30,000 people in the last week of July 2020 and was slated to be paid $1.95billion for 100million doses of the vaccine by the US government. The U.S. deal priced two doses at $39, and the company stated that it would not lower the rates for other countries until the outbreak is no longer a pandemic. Pfizer's CEO stated the companies in the private sector producing a vaccine should make a profit. In September 2020, Pfizer and BioNTech announced that they had completed talks with the European Commission to provide an initial 200million vaccine doses to the EU, with the option to supply another 100million doses at a later date.


title: Pfizer

text: On November 9, 2020, Pfizer announced that BioNTech's COVID-19 vaccine, tested on 43,500 people, was found to be 90% effective at preventing symptomatic COVID-19. The efficacy was updated to 95% a week later. Akiko Iwasaki, an immunologist interviewed by the "New York Times", described the efficacy figure as "really a spectacular number." The announcement made Pfizer and BioNTech the first companies to develop and test a working vaccine for COVID-19.


title: Pfizer

text: Over the following month and a half, regulators in various countries approved Pfizer's vaccine for emergency use. The United Kingdom approved the vaccine first, on December 2, followed by Bahrain on December 4, Canada on December 9, and Saudi Arabia on December 10. On December 10, 2020, the United States FDA held an advisory committee meeting to discuss authorization of the vaccine. The next day, the US officially became the 5th country to approve use of Pfizer's vaccine under an Emergency Use Authorization (EUA), with an independent panel voting 17–4 in support of approval. On December 14, Singapore became one of the first in Asia to approve the vaccine through the Health Sciences Authority. On December 21, the European Medicines Agency (EMA) recommended granting a conditional marketing authorisation for the vaccine in the European Union, under the brand name "Comirnaty."


title: Pfizer

text: As of early May 2021, Pfizer and BioNTech had manufactured at least 430 million vaccine doses, which have been distributed to 91 countries and territories. The companies have said they expect to manufacture nearly 3 billion total vaccine doses in 2021. Pfizer provided 0.9% Sodium chloride Injection USP diluent for use with the Pfizer–BioNTech COVID-19 vaccine under the name of its subsidiary, Hospira. Pfizer also purchased large quantities of single-use medical and surgical gloves and protective bodysuits from Ansell during the process, contributing to a doubling of the supplier's manufacturing capacity.


title: Pfizer

text: In February 2021, after a year long investigation relying on unnamed officials, Pfizer was accused by The Bureau of Investigative Journalism (TBIJ) of employing "high-level bullying" against at least two Latin American countries during negotiations to acquire COVID-19 vaccines, including requesting that the countries put sovereign assets as collateral for payments. According to TBIJ, these negotiation tactics resulted in a months long delay in Pfizer reaching a vaccine agreement with one country and a complete failure to reach agreements with two other countries, including Argentina and Brazil.


title: Pfizer

text: On 2 November 2021, TBMJ published an article after obtaining information from a whistleblower from the Ventavia Research Group. Ventavia was hired by Pfizer as a research subcontractor. The company falsified data, unblinded patients, employed inadequately trained vaccinators, and was slow to follow up on adverse events reported in Pfizer's pivotal phase III trial. The regional director, Brook Jackson, emailed a complaint to the US Food and Drug Administration (FDA). Ventavia fired her later the same day. The European Medicines Agency (EMA) stated in a response to the European Parliament, that "the deficiencies identified do not jeopardize the quality and integrity of the data from the main Comirnaty trial and have no impact on the benefit-risk assessment or on the conclusions on the safety, effectiveness and quality of the vaccine".


title: Pfizer

text: On 10 October 2022, during a session of the European Parliament's Special Committee on the COVID-19 Pandemic, Pfizer executive Janine Small testified that the company had not evaluated their COVID-19 vaccine for its ability to reduce transmission of the SARS-CoV-2 virus prior to its release to the general public. Dutch MEP Rob Roos described the admission as "scandalous". CEO Albert Bourla was slated to attend, but withdrew. Roos' statements in turn have been described as "misleading".


title: Pfizer

text: In November 2021, Pfizer launched a new COVID-19 oral antivirus treatment known as Paxlovid. In January 2022, the Pfizer CEO Albert Bourla confirmed that the trial results of a fourth dose were pending until March 2022. He said that the firm was setting up a collaboration to develop an anti-COVID pill treatment along with a French company, Novasep. He also said the COVID vaccine was "safe and efficient" for children. In May 2022, reports emerged of patients experiencing "rebound" symptoms after completing a five-day course of Paxlovid. The FDA responded by announcing they had performed additional analyses of the drug's clinical trial data, and decided against changing its recommendations. U.S. President Joe Biden and Dr. Anthony Fauci were both reported to experience this rebound syndrome in the months that followed, while continuing to recommend the drug for those who may benefit from it.


title: Pfizer

text: In 1993, the Food and Drug Administration (FDA) approved gabapentin only for treatment of seizures. Warner–Lambert, which merged with Pfizer in 2000, used continuing medical education and medical research, sponsored articles about the drug for the medical literature, and alleged suppression of unfavorable study results, to promote gabapentin. Within five years, the drug was being widely used for off-label uses such as treatment of pain and psychiatric conditions. Warner–Lambert admitted to violating FDA regulations by promoting the drug for pain, psychiatric conditions, migraine, and other unapproved uses. In 2004, the company paid $430million in one of the largest settlements to resolve criminal and civil health care liability charges. It was the first off-label promotion case successfully brought under the False Claims Act. A Cochrane review concluded that gabapentin is ineffective in migraine prophylaxis. The American Academy of Neurology rates it as having unproven efficacy, while the Canadian Headache Society and the European Federation of Neurological Societies rate its use as being supported by moderate and low-quality evidence.


title: Pfizer

text: In September 2009, Pfizer pleaded guilty to the illegal marketing of arthritis drug valdecoxib ("Bextra") and agreed to a $2.3billion settlement, the largest health care fraud settlement at that time. Pfizer promoted the sale of the drug for several uses and dosages that the Food and Drug Administration specifically declined to approve due to safety concerns. The drug was pulled from the market in 2005. It was Pfizer's fourth such settlement in a decade. The payment included $1.195billion in criminal penalties for felony violations of the Federal Food, Drug, and Cosmetic Act, and $1.0billion to settle allegations it had illegally promoted the drugs for uses that were not approved by the Food and Drug Administration (FDA) leading to violations under the False Claims Act as reimbursements were requested from Federal and State programs. The criminal fine was the largest ever assessed in the United States to date. Pfizer entered a corporate integrity agreement with the Office of Inspector General that required it to make substantial structural reforms within the company, and publish to its website its post approval commitments and a searchable database of all payments to physicians made by the company.


title: Pfizer

text: Peter Rost was vice president in charge of the endocrinology division at Pharmacia before its acquisition by Pfizer. During that time he raised concerns internally about kickbacks and off-label marketing of Genotropin, Pharmacia's human growth hormone drug. Pfizer reported the Pharmacia marketing practices to the FDA and Department of Justice; Rost was unaware of this and filed an FCA lawsuit against Pfizer. Pfizer kept him employed, but isolated him until the FCA suit was unsealed in 2005. The Justice Department declined to intervene, and Pfizer fired him, and he filed a wrongful termination suit against Pfizer. Pfizer won a summary dismissal of the case, with the court ruling that the evidence showed Pfizer had decided to fire Rost prior to learning of his whistleblower activities.


title: Pfizer

text: A "whistleblower suit" was filed in 2005 against Wyeth, which was acquired by Pfizer in 2009, alleging that the company illegally marketed sirolimus ("Rapamune") for off-label uses, targeted specific doctors and medical facilities to increase sales of Rapamune, tried to get transplant patients to change from their transplant drugs to Rapamune, and specifically targeted African-Americans. According to the whistleblowers, Wyeth also provided doctors and hospitals that prescribed the drug with kickbacks such as grants, donations, and other money. In 2013, the company pleaded guilty to criminal mis-branding violations under the Federal Food, Drug, and Cosmetic Act. By August 2014, it had paid $491million in civil and criminal penalties related to Rapamune.


title: Pfizer

text: In June 2010, health insurance network Blue Cross Blue Shield (BCBS) filed a lawsuit against Pfizer for allegedly illegally marketing drugs Bextra, Geodon and Lyrica. BCBS alleged that Pfizer used kickbacks and wrongly persuaded doctors to prescribe the drugs. According to the lawsuit, Pfizer handed out 'misleading' materials on off-label uses, sent over 5,000 doctors on trips to the Caribbean or around the United States, and paid them $2,000 honoraria in return for listening to lectures about Bextra. Despite Pfizer's claims that "the company's intent was pure" in fostering a legal exchange of information among doctors, an internal marketing plan revealed that Pfizer intended to train physicians "to serve as public relations spokespeople." The case was settled in 2014 for $325million. Fearing that Pfizer is "too big to fail" and that prosecuting the company would result in disruptions to Medicare and Medicaid, federal prosecutors instead charged a subsidiary of a subsidiary of a subsidiary of Pfizer, which is "nothing more than a shell company whose only function is to plead guilty."


title: Pfizer

text: According to "Harper's Magazine" publisher John R. MacArthur, Pfizer withdrew "between $400,000 and a million dollars" worth of ads from "Harper's Magazine" following an unflattering article on depression medication.


title: Pfizer

text: The Quigley Company, which sold asbestos-containing insulation products until the early 1970s, was acquired by Pfizer in 1968. In June 2013, asbestos victims and Pfizer negotiated a settlement that required Pfizer to pay a total of $964million: $430million to 80% of existing plaintiffs and place an additional $535million into a settlement trust that will compensate future plaintiffs as well as the remaining 20% of plaintiffs with claims against Pfizer and Quigley. Of that $535million, $405million is in a 40-year note from Pfizer, while $100million is from insurance policies.


title: Pfizer

text: Pfizer purchased Shiley in 1979, at the onset of its Convexo-Concave valve ordeal, involving the Bjork–Shiley valve. Approximately 500 people died when defective heart valves fractured and, in 1994, Pfizer agreed to pay $10.75million to settle claims by the United States Department of Justice that the company lied to get approval for the valves.


title: Pfizer

text: A federal lawsuit was filed by a scientist claiming she got an infection by a genetically modified lentivirus while working for Pfizer, resulting in intermittent paralysis. A judge dismissed the case citing a lack of evidence that the illness was caused by the virus but the jury ruled that by firing the employee, Pfizer violated laws protecting freedom of speech and whistleblowers and awarded her $1.37million.


title: Pfizer

text: Brigham Young University (BYU) said a professor of chemistry, Dr. Daniel L. Simmons, discovered an enzyme in the 1990s that led towards development of Celebrex. BYU was originally seeking a 15% royalty on sales, equating to $9.7billion. A research agreement had been made between BYU and Monsanto, whose pharmaceutical business was later acquired by Pfizer, to develop a better aspirin. The enzyme Dr. Simmons claims to have discovered would induce pain and inflammation while causing gastrointestinal problems and Celebrex is used to reduce those issues. A six-year battle ensued because BYU claimed that Pfizer did not give Dr. Simmons credit or compensation, while Pfizer claimed that it had met all obligations regarding the Monsanto agreement. In May 2012, Pfizer settled the allegations, agreeing to pay $450million.


title: Pfizer

text: In 1996, an outbreak of measles, cholera, and bacterial meningitis occurred in Nigeria. Pfizer representatives and personnel from a contract research organization (CRO) traveled to Kano to set up a clinical trial and administer an experimental antibiotic, trovafloxacin, to approximately 200 children. Local Kano officials reported that more than fifty children died in the experiment, while many others developed mental and physical deformities. The nature and frequency of both fatalities and other adverse outcomes were similar to those historically found among pediatric patients treated for meningitis in sub-Saharan Africa. In 2001, families of the children, as well as the governments of Kano and Nigeria, filed lawsuits regarding the treatment. According to "Democracy Now!", "[r]esearchers did not obtain signed consent forms, and medical personnel said Pfizer did not tell parents their children were getting the experimental drug." The lawsuits also accused Pfizer of using the outbreak to perform unapproved human testing, as well as allegedly under-dosing a control group being treated with traditional antibiotics in order to skew the results of the trial in favor of Trovan. Nigerian medical personnel as well as at least one Pfizer physician said the trial was conducted without regulatory approval.


title: Pfizer

text: In 2007, Pfizer published a Statement of Defense letter. The letter stated that the drug's oral form was safer and easier to administer, that Trovan had been used safely in more than five thousand Americans prior to the Nigerian trial, that mortality in the patients treated by Pfizer was lower than that observed historically in African meningitis epidemics, and that no unusual side effects, unrelated to meningitis, were observed after four weeks.


title: Pfizer

text: In June 2010, the US Supreme Court rejected Pfizer's appeal against a ruling allowing lawsuits by the Nigerian families to proceed.


title: Pfizer

text: In December 2010, a United States diplomatic cables leak was released by WikiLeaks indicating that Pfizer hired investigators to find evidence of corruption against Nigerian attorney general Aondoakaa to persuade him to drop legal action. "The Washington Post" reporter Joe Stephens, who helped break the story in 2000, called these actions "dangerously close to blackmail". In response, the company released a press statement describing the allegations as "preposterous" and saying that it acted in good faith. Aondoakka, who had allegedly demanded bribes from Pfizer in return for a settlement of the case, was declared unfit for office and had his U.S. visa revoked in association with corruption charges in 2010.


title: Pfizer

text: The lawsuits were eventually settled out of court. Pfizer committed to paying US$35 million "to compensate the families of children in the study", another US$30 million to "support healthcare initiatives in Kano", and 10 million to cover legal costs. Payouts began in 2011.


title: Pfizer

text: In July 2022, UK antitrust authorities fined Pfizer £63 million for unfairly high priced drug that aids in controlling epileptic seizures. The Competition and Markets Authority stated that the company took advantage of loopholes by de-branding epilepsy drug Epanutin, by doing so the price of Epanutin's price was not regulated to the same standards the company are used to and therefore the price of the drug was raised. It was stated that over a four-year period, Pfizer had billed Epanutin for around 780% and 1,600% higher than its standard price.


title: Pfizer

text: In August 2022, Moderna announced that it will sue Pfizer and its partner BioNTech for infringing their patent on the mRNA technology.


title: Pfizer

text: In 2012, the company was named to the Carbon Disclosure Project's Carbon Leadership Index in recognition of its efforts to reduce greenhouse gas emissions.


title: Pfizer

text: Pfizer has inherited Wyeth's liabilities in the American Cyanamid site in Bridgewater Township, New Jersey, a highly toxic EPA Superfund site. Pfizer has since attempted to remediate this land in order to clean and develop it for future profits and potential public uses. The Sierra Club and the Edison Wetlands Association have opposed the cleanup plan, arguing that the area is subject to flooding, which could cause pollutants to leach. The EPA considers the plan the most reasonable from considerations of safety and cost-effectiveness, arguing that an alternative plan involving trucking contaminated soil off site could expose cleanup workers. The EPA's position is backed by the environmental watchdog group CRISIS.


title: Pfizer

text: In June 2002, a chemical explosion at the Groton plant injured 7 people and caused the evacuation of more than 100 homes in the surrounding area.


title: Pfizer

text: Pfizer engages with the public and private sectors in a variety of settings including to promote research and development, academic funding, event sponsorship, philanthropy, and political lobbying.


title: Pfizer

text: During the COVID-19 pandemic, Pfizer engaged many forms of media to promote their COVID-19 vaccine, including a commissioned National Geographic documentary. Pfizer is also a donor to the National Geographic Society.


title: Pfizer

text: Pfizer has been a major donor to the National Press Foundation. Pfizer sponsored a program for the NPF called "Cancer Issues 2010" to train journalists to "understand the latest research" on various cancers, including the role of pharmaceutical products and vaccines. MicroRNA (miRNA) was also a listed topic.


title: Pfizer

text: Pfizer sponsors 19 to Zero, a "coalition of academics, public health experts, behavioural economists, and creative professionals" that develops media and educational materials to influence public perception surrounding COVID-19 and COVID-19 vaccines.


title: Pfizer

text: Pfizer is affiliated with a variety of industry organizations engaging in political lobbying, and has made substantial direct donations to government and regulatory agencies:


title: Pfizer

text: Scott Gottlieb, who resigned as FDA commissioner in April 2019, joined the Pfizer board of directors three months later, in July 2019.


title: Pfizer

text: Pfizer lobbied various officials in the Government of British Columbia between April and November 2012, including then-premier Christy Clark, future premier John Horgan, future health minister Adrian Dix, and future deputy premier, minister of public safety and solicitor general Mike Farnworth. The disclosed purpose was to "provide health policy and pharmaceutical information and communications on behalf of Pfizer Canada," and "learn and understand the budgetary, policy and strategic directions of the Government."


title: Pfizer

text: Pfizer has engaged in a number of public health and global health initiatives worldwide, and provides funding for health care facilities of various specialties in Canada and the United States:


title: Pfizer

text: Pfizer sponsored a presentation in January 2020 delivered by Julie Bettinger through British Columbia's Provincial Health Services Authority (PHSA) titled "Vaccine hesitancy: It doesn't matter if the vaccine works if nobody gets it."


title: Pfizer

text: In 2020, Pfizer provided funding in the range of $100,000.00 - $250,000.00 to Ronald McDonald House Charities “to provide resources that directly improve the health and well-being of children and their families.”


title: Pfizer

text: Pfizer has partnered with and sponsored many medical research networks and professional associations in the United States, Canada and globally:


title: DVD

text: The DVD (common abbreviation for Digital Video Disc or Digital Versatile Disc) is a digital optical disc data storage format. It was invented and developed in 1995 and first released on November 1, 1996, in Japan. The medium can store any kind of digital data and has been widely used for video programs (watched using DVD players) or formerly for storing software and other computer files as well. DVDs offer significantly higher storage capacity than compact discs (CD) while having the same dimensions. A standard DVD can store up to 4.7 GB of storage, while variants can store up to a maximum of 17.08 GB.


title: DVD

text: Prerecorded DVDs are mass-produced using molding machines that physically stamp data onto the DVD. Such discs are a form of DVD-ROM because data can only be read and not written or erased. Blank recordable DVD discs (DVD-R and DVD+R) can be recorded once using a DVD recorder and then function as a DVD-ROM. Rewritable DVDs (DVD-RW, DVD+RW, and DVD-RAM) can be recorded and erased many times.


title: DVD

text: DVDs are used in DVD-Video consumer digital video format and less commonly in DVD-Audio consumer digital audio format, as well as for authoring DVD discs written in a special AVCHD format to hold high definition material (often in conjunction with AVCHD format camcorders). DVDs containing other types of information may be referred to as DVD data discs.


title: DVD

text: The "Oxford English Dictionary" comments that, "In 1995, rival manufacturers of the product initially named digital video disc agreed that, in order to emphasize the flexibility of the format for multimedia applications, the preferred abbreviation DVD would be understood to denote digital versatile disc." The OED also states that in 1995, "The companies said the official name of the format will simply be DVD. Toshiba had been using the name 'digital video disc', but that was switched to 'digital versatile disc' after computer companies complained that it left out their applications."


title: DVD

text: "Digital versatile disc" is the explanation provided in a DVD Forum Primer from 2000 and in the DVD Forum's mission statement, which the purpose is to promote broad acceptance of DVD products on technology, across entertainment, and other industries.


title: DVD

text: Because DVDs became highly popular for the distribution of movies in the 2000s, the term "DVD" became popularly used in English as a noun to describe specifically a full-length movie released on the format; for example the sentence to "watch a DVD" describes watching a movie on DVD.


title: DVD

text: Released in 1987, CD Video used analog video encoding on optical discs matching the established standard size of audio CDs. Video CD (VCD) became one of the first formats for distributing "digitally" encoded films in this format, in 1993. In the same year, two new optical disc storage formats were being developed. One was the Multimedia Compact Disc (MMCD), backed by Philips and Sony (developers of the CD and CD-i), and the other was the Super Density (SD) disc, supported by Toshiba, Time Warner, Matsushita Electric, Hitachi, Mitsubishi Electric, Pioneer, Thomson, and JVC. By the time of the press launches for both formats in January 1995, the MMCD nomenclature had been dropped, and Philips and Sony were referring to their format as Digital Video Disc (DVD).


title: DVD

text: On May 3, 1995, an ad hoc, technical working group formed from five computer companies (IBM, Apple, Compaq, Hewlett-Packard, and Microsoft) issued a press release stating that they would only accept a single format. The TWG voted to boycott both formats unless the two camps agreed on a single, converged standard. They recruited Lou Gerstner, president of IBM, to pressure the executives of the warring factions. In one significant compromise, the MMCD and SD groups agreed to adopt proposal SD 9, which specified that both layers of the dual-layered disc be read from the same side—instead of proposal SD 10, which would have created a two-sided disc that users would have to turn over. As a result, the DVD specification provided a storage capacity of 4.7 GB (4.38 GiB) for a single-layered, single-sided disc and 8.5 GB (7.92 GiB) for a dual-layered, single-sided disc. The DVD specification ended up similar to Toshiba and Matsushita's Super Density Disc, except for the dual-layer option. MMCD was single-sided and optionally dual-layer, whereas SD was two half-thickness, single-layer discs which were pressed separately and then glued together to form a double-sided disc.


title: DVD

text: Philips and Sony decided that it was in their best interests to end the format war, and on September 15, 1995 agreed to unify with companies backing the Super Density Disc to release a single format, with technologies from both. After other compromises between MMCD and SD, the computer companies through TWG won the day, and a single format was agreed upon. The TWG also collaborated with the Optical Storage Technology Association (OSTA) on the use of their implementation of the ISO-13346 file system (known as Universal Disk Format) for use on the new DVDs. The format's details were finalized on December 8, 1995.


title: DVD

text: In November 1995, Samsung announced it would start mass-producing DVDs by September 1996. The format launched on November 1, 1996, in Japan, mostly with music video releases. The first major releases from Warner Home Video arrived on December 20, 1996, with four titles being available. The format's release in the U.S. was delayed multiple times, from August 1996, to October 1996, November 1996, before finally settling on early 1997. Players began to be produced domestically that winter, with March 24, 1997 as the U.S. launch date of the format proper in seven test markets. Approximately 32 titles were available on launch day, mainly from the Warner, MGM, and New Line libraries. However, the launch was planned for the following day (March 25), leading to a distribution change with retailers and studios to prevent similar violations of breaking the street date. The nationwide rollout for the format happened on August 22, 1997.


title: DVD

text: DTS announced in late 1997 that they would be coming onto the format. The sound system company revealed details in a November 1997 online interview, and clarified it would release discs in early 1998. However, this date would be pushed back several times before finally releasing their first titles at the 1999 Consumer Electronics Show.


title: DVD

text: Movie and home entertainment distributors adopted the DVD format to replace the ubiquitous VHS tape as the primary consumer video distribution format.


title: DVD

text: Immediately following the formal adoption of a unified standard for DVD, two of the four leading video game console companies (Sega and The 3DO Company) said they already had plans to design a gaming console with DVDs as the source medium. Sony stated at the time that they had no plans to use DVD in their gaming systems, despite being one of the developers of the DVD format and eventually the first company to actually release a DVD-based console. Game consoles such as the PlayStation 2, Xbox, and Xbox 360 use DVDs as their source medium for games and other software. Contemporary games for Windows were also distributed on DVD. Early DVDs were mastered using DLT tape, but using DVD-R DL or +R DL eventually became common. TV DVD combos, combining a standard definition CRT TV or an HD flat panel TV with a DVD mechanism under the CRT or on the back of the flat panel, and VCR/DVD combos were also available for purchase.


title: DVD

text: For consumers, DVD soon replaced VHS as the favored choice for home movie releases. In the year 2001, DVD players outsold VCRs for the first time in the United States. At this time 1 in 4 American households owned a DVD player. By 2007, about 80% of Americans owned a DVD player, a figure that had surpassed VCRs and was also higher than personal computers or cable television.


title: DVD

text: The DVD specifications created and updated by the DVD Forum are published as so-called "DVD Books" (e.g. DVD-ROM Book, DVD-Audio Book, DVD-Video Book, DVD-R Book, DVD-RW Book, DVD-RAM Book, DVD-AR (Audio Recording) Book, DVD-VR (Video Recording) Book, etc.). DVD discs are made up of two discs; normally one is blank, and the other contains data. Each disc is 0.6 mm thick, and are glued together to form a DVD disc. The gluing process must be done carefully to make the disc as flat as possible to avoid both birefringence and "disc tilt", which is when the disc is not perfectly flat, preventing it from being read.


title: DVD

text: Some specifications for mechanical, physical and optical characteristics of DVD optical discs can be downloaded as freely available standards from the ISO website. There are also equivalent European Computer Manufacturers Association (Ecma) standards for some of these specifications, such as Ecma-267 for DVD-ROMs. Also, the DVD+RW Alliance publishes competing recordable DVD specifications such as DVD+R, DVD+R DL, DVD+RW or DVD+RW DL. These DVD formats are also ISO standards.


title: DVD

text: Some DVD specifications (e.g. for DVD-Video) are not publicly available and can be obtained only from the DVD Format/Logo Licensing Corporation (DVD FLLC) for a fee of US$5000. Every subscriber must sign a non-disclosure agreement as certain information on the DVD Books is proprietary and confidential.


title: DVD

text: Borrowing from the LaserDisc format, the DVD standard includes DVD-10 discs (Type B in ISO) with two recorded data layers such that only one layer is accessible from either side of the disc. This doubles the total nominal capacity of a DVD-10 disc to 9.4 GB (8.75 GiB), but each side is locked to 4.7 GB. Like DVD-5 discs, DVD-10 discs are defined as single-layer (SL) discs.


title: DVD

text: DVD hardware accesses the additional layer (layer 1) by refocusing the laser through an otherwise normally-placed, semitransparent first layer (layer 0). This laser refocus—and the subsequent time needed to reacquire laser tracking—can cause a noticeable pause in A/V playback on earlier DVD players, the length of which varies between hardware. A printed message explaining that the layer-transition pause was not a malfunction became standard on DVD keep cases. During mastering, a studio could make the transition less obvious by timing it to occur just before a camera angle change or other abrupt shift, an early example being the DVD release of Toy Story. Later in the format's life, larger data buffers and faster optical pickups in DVD players made layer transitions effectively invisible regardless of mastering.


title: DVD

text: The DVD Book also permits an additional disc type called DVD-14: a hybrid double-sided disc with one dual-layer side, one single-layer side, and a total nominal capacity of 12.3 GB. DVD-14 has no counterpart in ISO.


title: DVD

text: Both of these additional disc types are extremely rare due to their complicated and expensive manufacturing. For this reason, some DVDs that were initially issued as double-sided discs were later pressed as two-disc sets.


title: DVD

text: HP initially developed recordable DVD media from the need to store data for backup and transport. DVD recordables are now also used for consumer audio and video recording. Three formats were developed: DVD-R/RW, DVD+R/RW (plus), and DVD-RAM. DVD-R is available in two formats, General (650 nm) and Authoring (635 nm), where Authoring discs may be recorded with CSS encrypted video content but General discs may not.


title: DVD

text: Dual-layer recording (occasionally called double-layer recording) allows DVD-R and DVD+R discs to store nearly double the data of a single-layer disc—8.5 and 4.7 gigabyte capacities, respectively. The additional capacity comes at a cost: DVD±DLs have slower write speeds as compared to DVD±R. DVD-R DL was developed for the DVD Forum by Pioneer Corporation; DVD+R DL was developed for the DVD+RW Alliance by Mitsubishi Kagaku Media (MKM) and Philips.


title: DVD

text: Recordable DVD discs supporting dual-layer technology are backward-compatible with some hardware developed before the recordable medium.


title: DVD

text: DVD drives are devices that can read DVD discs on a computer. DVD players are a particular type of devices that do not require a computer to work, and can read DVD-Video and DVD-Audio discs.


title: DVD

text: Read and write speeds for the first DVD drives and players were 1,385 kB/s (1,353 KiB/s); this speed is usually called "1×". More recent models, at 18× or 20×, have 18 or 20 times that speed. Note that for CD drives, 1× means 153.6 kB/s (150 KiB/s), about one-ninth as swift.


title: DVD

text: DVD recordable and rewritable discs can be read and written using either constant angular velocity (CAV), constant linear velocity (CLV), Partial constant angular velocity (P-CAV) or Zoned Constant Linear Velocity (Z-CLV or ZCLV).


title: DVD

text: Due to the slightly lower data density of dual layer DVDs (4.25 GB instead of 4.7 GB per layer), the required rotation speed is around 10% faster for the same data rate, which means that the same angular speed rating equals a 10% higher physical angular rotation speed. For that reason, the increase of reading speeds of dual layer media has stagnated at 12× (constant angular velocity) for half-height optical drives released since around 2005, and slim type optical drives are only able to record dual layer media at 6× (constant angular velocity), while reading speeds of 8× are still supported by such.


title: DVD

text: The quality and data integrity of optical media is measureable, which means that future data losses caused by deteriorating media can be predicted well in advance by measuring the rate of correctable data errors.


title: DVD

text: DVD-Video is a standard for distributing video/audio content on DVD media. The format went on sale in Japan on November 1, 1996, in the United States on March 24, 1997, to line up with the 69th Academy Awards that day; in Canada, Central America, and Indonesia later in 1997, and in Europe, Asia, Australia, and Africa in 1998. DVD-Video became the dominant form of home video distribution in Japan when it first went on sale on November 1, 1996, but it shared the market for home video distribution in the United States for several years; it was June 15, 2003, when weekly DVD-Video in the United States rentals began outnumbering weekly VHS cassette rentals.


title: DVD

text: DVD-Video is still the dominant form of home video distribution worldwide except for in Japan where it was surpassed by Blu-ray Disc when Blu-ray first went on sale in Japan on March 31, 2006.


title: DVD

text: In 2006, two new formats called HD DVD and Blu-ray Disc were released as the successor to DVD. HD DVD competed unsuccessfully with Blu-ray Disc in the format war of 2006–2008. A dual layer HD DVD can store up to 30 GB and a dual layer Blu-ray disc can hold up to 50 GB.


title: DVD

text: However, unlike previous format changes, e.g., vinyl to Compact Disc or VHS videotape to DVD, there is no immediate indication that production of the standard DVD will gradually wind down, as they still dominate, with around 75% of video sales and approximately one billion DVD player sales worldwide as of April 2011. In fact, experts claim that the DVD will remain the dominant medium for at least another five years as Blu-ray technology is still in its introductory phase, write and read speeds being poor and necessary hardware being expensive and not readily available.


title: DVD

text: Consumers initially were also slow to adopt Blu-ray due to the cost. By 2009, 85% of stores were selling Blu-ray Discs. A high-definition television and appropriate connection cables are also required to take advantage of Blu-ray disc. Some analysts suggest that the biggest obstacle to replacing DVD is due to its installed base; a large majority of consumers are satisfied with DVDs.


title: DVD

text: DVDs are also facing competition from video on demand services. With increasing numbers of homes having high speed Internet connections, many people now have the option to either rent or buy video from an online service, and view it by streaming it directly from that service's servers, meaning they no longer need any form of permanent storage media for video at all. By 2017, digital streaming services had overtaken the sales of DVDs and Blu-rays for the first time.


title: DVD

text: Manufacturers continue to release standard DVD titles , and the format remains the preferred one for the release of older television programs and films. Shows that were shot and edited entirely on film, such as "", cannot be released in high definition without being re-scanned from the original film recordings. Shows that were made between the early 1980s and the early 2000s were generally shot on film, then transferred to video tape, and then edited natively in either NTSC or PAL, making high-definition transfers impossible as these SD standards were baked into the final cuts of the episodes. "" is the only such show that has a Blu-ray release, as prints were re-scanned and edited from the ground up.


title: DVD

text: Longevity of a storage medium is measured by how long the data remains readable, assuming compatible devices exist that can read it: that is, how long the disc can be stored until data is lost. Numerous factors affect longevity: composition and quality of the media (recording and substrate layers), humidity and light storage conditions, the quality of the initial recording (which is sometimes a matter of mutual compatibility of media and recorder), etc. According to NIST, "[a] temperature of 64.4 °F (18 °C) and 40% RH [Relative Humidity] would be considered suitable for long-term storage. A lower temperature and RH is recommended for extended-term storage."


title: DVD

text: As with CDs, the information and data storage will begin to degrade over time with most standard DVDs lasting up to 30 years depending the type of environment they are stored and whether they are full with data.


title: DVD

text: According to the Optical Storage Technology Association (OSTA), "Manufacturers claim lifespans ranging from 30 to 100 years for DVD, DVD-R and DVD+R discs and up to 30 years for DVD-RW, DVD+RW and DVD-RAM."


title: DVD

text: According to a NIST/LoC research project conducted in 2005–2007 using accelerated life testing, "There were fifteen DVD products tested, including five DVD-R, five DVD+R, two DVD-RW and three DVD+RW types. There were ninety samples tested for each product. ... Overall, seven of the products tested had estimated life expectancies in ambient conditions of more than 45 years. Four products had estimated life expectancies of 30–45 years in ambient storage conditions. Two products had an estimated life expectancy of 15–30 years and two products had estimated life expectancies of less than 15 years when stored in ambient conditions." The life expectancies for 95% survival estimated in this project by type of product are tabulated below:


title: Danai Gurira

text: Danai Jekesai Gurira (; born February 14, 1978) is an American-Zimbabwean actress and playwright. She is best known for her starring roles as Michonne on the AMC horror drama series "The Walking Dead" (2012–2020, 2022) and as Okoye in the Marvel Cinematic Universe superhero films, "Black Panther" and "" (both in 2018), "" (2019), and "" (2022).


title: Danai Gurira

text: Gurira is also the playwright of the Broadway play "Eclipsed", for which she was nominated for a Tony Award for Best Play.


title: Danai Gurira

text: Gurira was born on February 14 1978 in Grinnell, Iowa, to Josephine Gurira, a college librarian, and Roger Gurira, a tenured professor in the Department of Chemistry at Grinnell College (both parents later joined the staff of University of Wisconsin–Platteville). Her parents moved from Southern Rhodesia, which is now Zimbabwe, to the United States in 1964. She is the youngest of four siblings; Shingai and Choni are her sisters and Tare, her brother, is a chiropractor. Gurira lived in Grinnell until December 1983, when at age five she and her family moved back to Harare, the capital of Zimbabwe, after Robert Mugabe rose to power in 1979.


title: Danai Gurira

text: She attended high school at Dominican Convent High School. Afterward, she returned to the United States to study at Macalester College in Saint Paul, Minnesota, graduating with a Bachelor of Arts in psychology. Gurira also earned a Master of Fine Arts in acting from New York University's Tisch School of the Arts.


title: Danai Gurira

text: Gurira taught playwriting and acting in Liberia, Zimbabwe and South Africa. One of her earliest notable performances occurred in 2001, as a senior at Macalester College. Gurira performed in a production of the Ntozake Shange play "For Colored Girls Who Have Considered Suicide / When the Rainbow Is Enuf", directed and choreographed by Dale Ricardo Shields. “She was a very intelligent, strong and independent young lady,” said Shields. “She approached her studies, her classes, with a lot of focus, and you can see the same things in her performance in ‘Black Panther.’ ”


title: Danai Gurira

text: Gurira said that she began writing plays in an effort to better utilize her strengths as an actress, and to tell stories that convey ideas about strong women with whom she identifies. As a playwright, she has been commissioned by Yale Repertory Theatre, Center Theatre Group, Playwrights Horizons, and the Royal Court.


title: Danai Gurira

text: Gurira co-wrote and co-starred in "In the Continuum", first at Woolly Mammoth Theatre Company and later Off-Broadway, which won her an Obie Award, an Outer Critics Circle Award, and a Helen Hayes Award for Best Lead Actress. In December 2011, "In the Continuum" commemorated World AIDS Day 2011. Sponsored by the United States Embassy in Zimbabwe, the play was performed at Harare's Theatre and featured the story of two women who were navigating the world after contracting HIV.


title: Danai Gurira

text: In 2009, Gurira made her acting debut on Broadway in August Wilson's play "Joe Turner's Come and Gone" playing Martha Pentecost.


title: Danai Gurira

text: Gurira's 2012 play "The Convert" was premiered as a co-production between the Goodman Theatre in Chicago and the McCarter Theatre in New Jersey. Later that year, Gurira received the Whiting Award for an emerging playwright.


title: Danai Gurira

text: In January 2015, "Familiar", a play written by Gurira and directed by Rebecca Taichman, opened at Yale Repertory Theatre. It later premiered Off-Broadway in New York at Playwrights Horizons. The play is about family, cultural identity, and the experience of life as a first-generation American, and Gurira has said that it was inspired in part by her family and friends.


title: Danai Gurira

text: In 2015, Lupita Nyong'o starred in Gurira's play, "Eclipsed" (2009), Off-Broadway at The Public Theater. It was announced that the play would move to Broadway in 2016 at the John Golden Theatre. It was the first play to premiere on Broadway with an all female and black cast and creative team. The play is set in war-torn Liberia and focuses on three women who are living as sex slaves to a rebel commander, as well as one of his former wives, and a relief worker, and follows and how they deal with this difficult situation. It starred Lupita Nyong'o, Akosua Busia, Saycon Sengbloh, Zainab Jah, and Pascale Armand and was directed by Liesl Tommy. The inspiration for Gurira's play was a photo of Colonel Black Diamond, a female freedom fighter from Liberia, in an article in "The New York Times". "Just to see these women standing there, you know, in their jeans and ... fashionable tops and their hair is all done, and they're all carrying AK-47s, was just an image I couldn't get out of my head." The image prompted curiosity about Liberia's fourteen-year civil wars, as well as a research trip to Liberia in 2007. Gurira interviewed more than 30 women who had been raped, among whose daughters that had been taken by rebel fighters and turned into sex slaves. She also spoke to female peace activists who were instrumental in ending the violence. The names of the women in "Eclipsed" come from the people Gurira met during her travels, whereas the fifth character is unnamed.


title: Danai Gurira

text: She received the 2016 Sam Norkin Award, for "Eclipsed" and "Familiar", presented by the Drama Desk Awards, which said, in part: "Danai Gurira demonstrates great insight, range and depth, bringing a fresh new voice to American theater." "Eclipsed" was nominated for the Tony Award for Best Play, and won the Tony Award for Best Costume Design in a Play.


title: Danai Gurira

text: Gurira starred in the drama film "The Visitor" in 2007, for which she won Method Fest Independent Film Festival Award for Best Supporting Actress. She appeared in the 2008 film "Ghost Town", the 2010 films "3 Backyards" and "My Soul to Take", and "Restless City" in 2011, as well as the television series "", "Life on Mars", and "Law & Order". From 2010 to 2011, she appeared in the HBO drama series "Treme".


title: Danai Gurira

text: In March 2012, AMC announced on a live broadcast that Gurira would join the cast of their horror-drama series "The Walking Dead", the highest rated series in cable television history, in its third season. Gurira plays Michonne, a relentless, katana-wielding character who joins a close-knit group in an apocalyptic world. Gurira had to learn how to ride horses for the series, which she enjoyed because it was a physical challenge. In February 2019, reports emerged that Gurira would be exiting the show once she had filmed her last episodes during the tenth season. Gurira's final episode, "What We Become" aired in March 2020, and by the time of her departure, she had been second billed in the opening credits.


title: Danai Gurira

text: In 2013, Gurira played a lead role in director Andrew Dosunmu's independent drama film "Mother of George", which premiered at 2013 Sundance Film Festival. Gurira received critical acclaim for her performance as a Nigerian woman struggling to live in the United States. In June 2013, Gurira won the Jean-Claude Gahd Dam award at the 2013 Guys Choice Awards.


title: Danai Gurira

text: Gurira played rapper Tupac Shakur's mother, Afeni Shakur, in "All Eyez on Me", a 2017 biopic about the rap star. She then starred in Marvel's film "Black Panther", which was released in February 2018. She played Okoye, the head of the Dora Milaje, the personal bodyguards of the Black Panther, and received critical acclaim for her performance. Gurira reprised Okoye in "" (2018), "" (2019), and "" (2022). In 2020, she signed a deal with ABC Studios.


title: Danai Gurira

text: In 2008, Gurira appeared at the Global Green Sustainable Design Awards to read a letter written by a New Orleans native displaced by Hurricane Katrina.


title: Danai Gurira

text: In 2011, Gurira co-founded Almasi Arts, an organization dedicated to continuing arts education in Zimbabwe. Gurira currently serves as the Executive Artistic Director.


title: Danai Gurira

text: In 2015, Gurira signed an open letter begun by the ONE Campaign. The letter was addressed to Angela Merkel and Nkosazana Dlamini-Zuma, urging them to focus on women as they serve as the head of the G7 in Germany and the AU in South Africa respectively. The following year, Gurira founded the non-profit organization Love Our Girls, which aims to highlight the issues and challenges that specifically affect women throughout the world. In 2016, Gurira partnered with Johnson & Johnson in the fight against HIV/AIDS.


title: Danai Gurira

text: On December 2, 2018, Gurira was announced as a UN Women Goodwill Ambassador by UN Women Executive Director Phumzile Mlambo-Ngcuka at the Global Citizen Festival in Johannesburg, South Africa. As a UN Women Goodwill Ambassador, Gurira dedicates her support to putting a spotlight on gender equality and women's rights, as well as bringing unheard women's voices front and center.


title: Danai Gurira

text: Gurira is a Christian and lives in Los Angeles, though she regularly spends time in New York City. She identifies as a Zimbabwean-American. She speaks four languages: French, Shona, basic Xhosa, and English and stays physically fit through Pilates and cross training.


title: Photography

text: Photography is the art, application, and practice of creating durable images by recording light, either electronically by means of an image sensor, or chemically by means of a light-sensitive material such as photographic film. It is employed in many fields of science, manufacturing (e.g., photolithography), and business, as well as its more direct uses for art, film and video production, recreational purposes, hobby, and mass communication.


title: Photography

text: Typically, a lens is used to focus the light reflected or emitted from objects into a real image on the light-sensitive surface inside a camera during a timed exposure. With an electronic image sensor, this produces an electrical charge at each pixel, which is electronically processed and stored in a digital image file for subsequent display or processing. The result with photographic emulsion is an invisible latent image, which is later chemically "developed" into a visible image, either negative or positive, depending on the purpose of the photographic material and the method of processing. A negative image on film is traditionally used to photographically create a positive image on a paper base, known as a print, either by using an enlarger or by contact printing.


title: Photography

text: The word "photography" was created from the Greek roots φωτός ("phōtós"), genitive of φῶς ("phōs"), "light" and γραφή ("graphé") "representation by means of lines" or "drawing", together meaning "drawing with light".


title: Photography

text: Several people may have coined the same new term from these roots independently. Hercules Florence, a French painter and inventor living in Campinas, Brazil, used the French form of the word, "photographie", in private notes which a Brazilian historian believes were written in 1834. This claim is widely reported but is not yet largely recognized internationally. The first use of the word by the Franco-Brazilian inventor became widely known after the research of Boris Kossoy in 1980.


title: Photography

text: The German newspaper "Vossische Zeitung" of 25 February 1839 contained an article entitled "Photographie", discussing several priority claims – especially Henry Fox Talbot's – regarding Daguerre's claim of invention. The article is the earliest known occurrence of the word in public print. It was signed "J.M.", believed to have been Berlin astronomer Johann von Maedler. The astronomer Sir John Herschel is also credited with coining the word, independent of Talbot, in 1839.


title: Photography

text: The inventors Nicéphore Niépce, Henry Fox Talbot, and Louis Daguerre seem not to have known or used the word "photography", but referred to their processes as "Heliography" (Niépce), "Photogenic Drawing"/"Talbotype"/"Calotype" (Talbot), and "Daguerreotype" (Daguerre).


title: Photography

text: Photography is the result of combining several technical discoveries, relating to seeing an image and capturing the image. The discovery of the camera obscura ("dark chamber" in Latin) that provides an image of a scene dates back to ancient China. Greek mathematicians Aristotle and Euclid independently described a camera obscura in the 5th and 4th centuries BCE. In the 6th century CE, Byzantine mathematician Anthemius of Tralles used a type of camera obscura in his experiments.


title: Photography

text: The Arab physicist Ibn al-Haytham (Alhazen) (965–1040) also invented a camera obscura as well as the first true pinhole camera. The invention of the camera has been traced back to the work of Ibn al-Haytham. While the effects of a single light passing through a pinhole had been described earlier, Ibn al-Haytham gave the first correct analysis of the camera obscura, including the first geometrical and quantitative descriptions of the phenomenon, and was the first to use a screen in a dark room so that an image from one side of a hole in the surface could be projected onto a screen on the other side. He also first understood the relationship between the focal point and the pinhole, and performed early experiments with afterimages, laying the foundations for the invention of photography in the 19th century.


title: Photography

text: Leonardo da Vinci mentions natural camerae obscurae that are formed by dark caves on the edge of a sunlit valley. A hole in the cave wall will act as a pinhole camera and project a laterally reversed, upside down image on a piece of paper. Renaissance painters used the camera obscura which, in fact, gives the optical rendering in color that dominates Western Art. It is a box with a small hole in one side, which allows specific light rays to enter, projecting an inverted image onto a viewing screen or paper.


title: Photography

text: The birth of photography was then concerned with inventing means to capture and keep the image produced by the camera obscura. Albertus Magnus (1193–1280) discovered silver nitrate, and Georg Fabricius (1516–1571) discovered silver chloride, and the techniques described in Ibn al-Haytham's Book of Optics are capable of producing primitive photographs using medieval materials.


title: Photography

text: Daniele Barbaro described a diaphragm in 1566. Wilhelm Homberg described how light darkened some chemicals (photochemical effect) in 1694. The fiction book "Giphantie", published in 1760, by French author Tiphaigne de la Roche, described what can be interpreted as photography.


title: Photography

text: Around the year 1800, British inventor Thomas Wedgwood made the first known attempt to capture the image in a camera obscura by means of a light-sensitive substance. He used paper or white leather treated with silver nitrate. Although he succeeded in capturing the shadows of objects placed on the surface in direct sunlight, and even made shadow copies of paintings on glass, it was reported in 1802 that "the images formed by means of a camera obscura have been found too faint to produce, in any moderate time, an effect upon the nitrate of silver." The shadow images eventually darkened all over.


title: Photography

text: The first permanent photoetching was an image produced in 1822 by the French inventor Nicéphore Niépce, but it was destroyed in a later attempt to make prints from it. Niépce was successful again in 1825. In 1826 or 1827, he made the "View from the Window at Le Gras", the earliest surviving photograph from nature (i.e., of the image of a real-world scene, as formed in a camera obscura by a lens).


title: Photography

text: Because Niépce's camera photographs required an extremely long exposure (at least eight hours and probably several days), he sought to greatly improve his bitumen process or replace it with one that was more practical. In partnership with Louis Daguerre, he worked out post-exposure processing methods that produced visually superior results and replaced the bitumen with a more light-sensitive resin, but hours of exposure in the camera were still required. With an eye to eventual commercial exploitation, the partners opted for total secrecy.


title: Photography

text: Niépce died in 1833 and Daguerre then redirected the experiments toward the light-sensitive silver halides, which Niépce had abandoned many years earlier because of his inability to make the images he captured with them light-fast and permanent. Daguerre's efforts culminated in what would later be named the daguerreotype process. The essential elements—a silver-plated surface sensitized by iodine vapor, developed by mercury vapor, and "fixed" with hot saturated salt water—were in place in 1837. The required exposure time was measured in minutes instead of hours. Daguerre took the earliest confirmed photograph of a person in 1838 while capturing a view of a Paris street: unlike the other pedestrian and horse-drawn traffic on the busy boulevard, which appears deserted, one man having his boots polished stood sufficiently still throughout the several-minutes-long exposure to be visible. The existence of Daguerre's process was publicly announced, without details, on 7 January 1839. The news created an international sensation. France soon agreed to pay Daguerre a pension in exchange for the right to present his invention to the world as the gift of France, which occurred when complete working instructions were unveiled on 19 August 1839. In that same year, American photographer Robert Cornelius is credited with taking the earliest surviving photographic self-portrait.


title: Photography

text: In Brazil, Hercules Florence had apparently started working out a silver-salt-based paper process in 1832, later naming it "Photographie".


title: Photography

text: Meanwhile, a British inventor, William Fox Talbot, had succeeded in making crude but reasonably light-fast silver images on paper as early as 1834 but had kept his work secret. After reading about Daguerre's invention in January 1839, Talbot published his hitherto secret method and set about improving on it. At first, like other pre-daguerreotype processes, Talbot's paper-based photography typically required hours-long exposures in the camera, but in 1840 he created the calotype process, which used the chemical development of a latent image to greatly reduce the exposure needed and compete with the daguerreotype. In both its original and calotype forms, Talbot's process, unlike Daguerre's, created a translucent negative which could be used to print multiple positive copies; this is the basis of most modern chemical photography up to the present day, as daguerreotypes could only be replicated by rephotographing them with a camera. Talbot's famous tiny paper negative of the Oriel window in Lacock Abbey, one of a number of camera photographs he made in the summer of 1835, may be the oldest camera negative in existence.


title: Photography

text: In France, Hippolyte Bayard invented his own process for producing direct positive paper prints and claimed to have invented photography earlier than Daguerre or Talbot.


title: Photography

text: British chemist John Herschel made many contributions to the new field. He invented the cyanotype process, later familiar as the "blueprint". He was the first to use the terms "photography", "negative" and "positive". He had discovered in 1819 that sodium thiosulphate was a solvent of silver halides, and in 1839 he informed Talbot (and, indirectly, Daguerre) that it could be used to "fix" silver-halide-based photographs and make them completely light-fast. He made the first glass negative in late 1839.


title: Photography

text: In the March 1851 issue of "The Chemist", Frederick Scott Archer published his wet plate collodion process. It became the most widely used photographic medium until the gelatin dry plate, introduced in the 1870s, eventually replaced it. There are three subsets to the collodion process; the Ambrotype (a positive image on glass), the Ferrotype or Tintype (a positive image on metal) and the glass negative, which was used to make positive prints on albumen or salted paper.


title: Photography

text: Many advances in photographic glass plates and printing were made during the rest of the 19th century. In 1891, Gabriel Lippmann introduced a process for making natural-color photographs based on the optical phenomenon of the interference of light waves. His scientifically elegant and important but ultimately impractical invention earned him the Nobel Prize in Physics in 1908.


title: Photography

text: Glass plates were the medium for most original camera photography from the late 1850s until the general introduction of flexible plastic films during the 1890s. Although the convenience of the film greatly popularized amateur photography, early films were somewhat more expensive and of markedly lower optical quality than their glass plate equivalents, and until the late 1910s they were not available in the large formats preferred by most professional photographers, so the new medium did not immediately or completely replace the old. Because of the superior dimensional stability of glass, the use of plates for some scientific applications, such as astrophotography, continued into the 1990s, and in the niche field of laser holography, it has persisted into the 21st century.


title: Photography

text: Hurter and Driffield began pioneering work on the light sensitivity of photographic emulsions in 1876. Their work enabled the first quantitative measure of film speed to be devised.


title: Photography

text: The first flexible photographic roll film was marketed by George Eastman, founder of Kodak in 1885, but this original "film" was actually a coating on a paper base. As part of the processing, the image-bearing layer was stripped from the paper and transferred to a hardened gelatin support. The first transparent plastic roll film followed in 1889. It was made from highly flammable nitrocellulose known as nitrate film.


title: Photography

text: Although cellulose acetate or "safety film" had been introduced by Kodak in 1908, at first it found only a few special applications as an alternative to the hazardous nitrate film, which had the advantages of being considerably tougher, slightly more transparent, and cheaper. The changeover was not completed for X-ray films until 1933, and although safety film was always used for 16 mm and 8 mm home movies, nitrate film remained standard for theatrical 35 mm motion pictures until it was finally discontinued in 1951.


title: Photography

text: Films remained the dominant form of photography until the early 21st century when advances in digital photography drew consumers to digital formats. Although modern photography is dominated by digital users, film continues to be used by enthusiasts and professional photographers. The distinctive "look" of film based photographs compared to digital images is likely due to a combination of factors, including (1) differences in spectral and tonal sensitivity (S-shaped density-to-exposure (H&D curve) with film vs. linear response curve for digital CCD sensors), (2) resolution, and (3) continuity of tone.


title: Photography

text: Originally, all photography was monochrome, or "black-and-white". Even after color film was readily available, black-and-white photography continued to dominate for decades, due to its lower cost, chemical stability, and its "classic" photographic look. The tones and contrast between light and dark areas define black-and-white photography. Monochromatic pictures are not necessarily composed of pure blacks, whites, and intermediate shades of gray but can involve shades of one particular hue depending on the process. The cyanotype process, for example, produces an image composed of blue tones. The albumen print process, publicly revealed in 1847, produces brownish tones.


title: Photography

text: Many photographers continue to produce some monochrome images, sometimes because of the established archival permanence of well-processed silver-halide-based materials. Some full-color digital images are processed using a variety of techniques to create black-and-white results, and some manufacturers produce digital cameras that exclusively shoot monochrome. Monochrome printing or electronic display can be used to salvage certain photographs taken in color which are unsatisfactory in their original form; sometimes when presented as black-and-white or single-color-toned images they are found to be more effective. Although color photography has long predominated, monochrome images are still produced, mostly for artistic reasons. Almost all digital cameras have an option to shoot in monochrome, and almost all image editing software can combine or selectively discard RGB color channels to produce a monochrome image from one shot in color.


title: Photography

text: Color photography was explored beginning in the 1840s. Early experiments in color required extremely long exposures (hours or days for camera images) and could not "fix" the photograph to prevent the color from quickly fading when exposed to white light.


title: Photography

text: The first permanent color photograph was taken in 1861 using the three-color-separation principle first published by Scottish physicist James Clerk Maxwell in 1855. The foundation of virtually all practical color processes, Maxwell's idea was to take three separate black-and-white photographs through red, green and blue filters. This provides the photographer with the three basic channels required to recreate a color image. Transparent prints of the images could be projected through similar color filters and superimposed on the projection screen, an additive method of color reproduction. A color print on paper could be produced by superimposing carbon prints of the three images made in their complementary colors, a subtractive method of color reproduction pioneered by Louis Ducos du Hauron in the late 1860s.


title: Photography

text: Russian photographer Sergei Mikhailovich Prokudin-Gorskii made extensive use of this color separation technique, employing a special camera which successively exposed the three color-filtered images on different parts of an oblong plate. Because his exposures were not simultaneous, unsteady subjects exhibited color "fringes" or, if rapidly moving through the scene, appeared as brightly colored ghosts in the resulting projected or printed images.


title: Photography

text: Implementation of color photography was hindered by the limited sensitivity of early photographic materials, which were mostly sensitive to blue, only slightly sensitive to green, and virtually insensitive to red. The discovery of dye sensitization by photochemist Hermann Vogel in 1873 suddenly made it possible to add sensitivity to green, yellow and even red. Improved color sensitizers and ongoing improvements in the overall sensitivity of emulsions steadily reduced the once-prohibitive long exposure times required for color, bringing it ever closer to commercial viability.


title: Photography

text: Autochrome, the first commercially successful color process, was introduced by the Lumière brothers in 1907. Autochrome plates incorporated a mosaic color filter layer made of dyed grains of potato starch, which allowed the three color components to be recorded as adjacent microscopic image fragments. After an Autochrome plate was reversal processed to produce a positive transparency, the starch grains served to illuminate each fragment with the correct color and the tiny colored points blended together in the eye, synthesizing the color of the subject by the additive method. Autochrome plates were one of several varieties of additive color screen plates and films marketed between the 1890s and the 1950s.


title: Photography

text: Kodachrome, the first modern "integral tripack" (or "monopack") color film, was introduced by Kodak in 1935. It captured the three color components in a multi-layer emulsion. One layer was sensitized to record the red-dominated part of the spectrum, another layer recorded only the green part and a third recorded only the blue. Without special film processing, the result would simply be three superimposed black-and-white images, but complementary cyan, magenta, and yellow dye images were created in those layers by adding color couplers during a complex processing procedure.


title: Photography

text: Agfa's similarly structured Agfacolor Neu was introduced in 1936. Unlike Kodachrome, the color couplers in Agfacolor Neu were incorporated into the emulsion layers during manufacture, which greatly simplified the processing. Currently, available color films still employ a multi-layer emulsion and the same principles, most closely resembling Agfa's product.


title: Photography

text: Instant color film, used in a special camera which yielded a unique finished color print only a minute or two after the exposure, was introduced by Polaroid in 1963.


title: Photography

text: Color photography may form images as positive transparencies, which can be used in a slide projector, or as color negatives intended for use in creating positive color enlargements on specially coated paper. The latter is now the most common form of film (non-digital) color photography owing to the introduction of automated photo printing equipment. After a transition period centered around 1995–2005, color film was relegated to a niche market by inexpensive multi-megapixel digital cameras. Film continues to be the preference of some photographers because of its distinctive "look".


title: Photography

text: In 1981, Sony unveiled the first consumer camera to use a charge-coupled device for imaging, eliminating the need for film: the Sony Mavica. While the Mavica saved images to disk, the images were displayed on television, and the camera was not fully digital.


title: Photography

text: The first digital camera to both record and save images in a digital format was the Fujix DS-1P created by Fujfilm in 1988.


title: Photography

text: In 1991, Kodak unveiled the DCS 100, the first commercially available digital single lens reflex camera. Although its high cost precluded uses other than photojournalism and professional photography, commercial digital photography was born.


title: Photography

text: Digital imaging uses an electronic image sensor to record the image as a set of electronic data rather than as chemical changes on film. An important difference between digital and chemical photography is that chemical photography resists photo manipulation because it involves film and photographic paper, while digital imaging is a highly manipulative medium. This difference allows for a degree of image post-processing that is comparatively difficult in film-based photography and permits different communicative potentials and applications.


title: Photography

text: Digital photography dominates the 21st century. More than 99% of photographs taken around the world are through digital cameras, increasingly through smartphones.


title: Photography

text: A large variety of photographic techniques and media are used in the process of capturing images for photography. These include the camera; dualphotography; full-spectrum, ultraviolet and infrared media; light field photography; and other imaging techniques.


title: Photography

text: The camera is the image-forming device, and a photographic plate, photographic film or a silicon electronic image sensor is the capture medium. The respective recording medium can be the plate or film itself, or a digital magnetic or electronic memory.


title: Photography

text: Photographers control the camera and lens to "expose" the light recording material to the required amount of light to form a "latent image" (on plate or film) or RAW file (in digital cameras) which, after appropriate processing, is converted to a usable image. Digital cameras use an electronic image sensor based on light-sensitive electronics such as charge-coupled device (CCD) or complementary metal-oxide-semiconductor (CMOS) technology. The resulting digital image is stored electronically, but can be reproduced on a paper.


title: Photography

text: The camera (or 'camera obscura') is a dark room or chamber from which, as far as possible, all light is excluded except the light that forms the image. It was discovered and used in the 16th century by painters. The subject being photographed, however, must be illuminated. Cameras can range from small to very large, a whole room that is kept dark while the object to be photographed is in another room where it is properly illuminated. This was common for reproduction photography of flat copy when large film negatives were used (see Process camera).


title: Photography

text: As soon as photographic materials became "fast" (sensitive) enough for taking candid or surreptitious pictures, small "detective" cameras were made, some actually disguised as a book or handbag or pocket watch (the "Ticka" camera) or even worn hidden behind an Ascot necktie with a tie pin that was really the lens.


title: Photography

text: The movie camera is a type of photographic camera which takes a rapid sequence of photographs on recording medium. In contrast to a still camera, which captures a single snapshot at a time, the movie camera takes a series of images, each called a "frame". This is accomplished through an intermittent mechanism. The frames are later played back in a movie projector at a specific speed, called the "frame rate" (number of frames per second). While viewing, a person's eyes and brain merge the separate pictures to create the illusion of motion.


title: Photography

text: Photographs, both monochrome and color, can be captured and displayed through two side-by-side images that emulate human stereoscopic vision. Stereoscopic photography was the first that captured figures in motion. While known colloquially as "3-D" photography, the more accurate term is stereoscopy. Such cameras have long been realized by using film and more recently in digital electronic methods (including cell phone cameras).


title: Photography

text: Dualphotography consists of photographing a scene from both sides of a photographic device at once (e.g. camera for back-to-back dualphotography, or two networked cameras for portal-plane dualphotography). The dualphoto apparatus can be used to simultaneously capture both the subject and the photographer, or both sides of a geographical place at once, thus adding a supplementary narrative layer to that of a single image.


title: Photography

text: Ultraviolet and infrared films have been available for many decades and employed in a variety of photographic avenues since the 1960s. New technological trends in digital photography have opened a new direction in full spectrum photography, where careful filtering choices across the ultraviolet, visible and infrared lead to new artistic visions.


title: Photography

text: Modified digital cameras can detect some ultraviolet, all of the visible and much of the near infrared spectrum, as most digital imaging sensors are sensitive from about 350 nm to 1000 nm. An off-the-shelf digital camera contains an infrared hot mirror filter that blocks most of the infrared and a bit of the ultraviolet that would otherwise be detected by the sensor, narrowing the accepted range from about 400 nm to 700 nm.


title: Photography

text: Replacing a hot mirror or infrared blocking filter with an infrared pass or a wide spectrally transmitting filter allows the camera to detect the wider spectrum light at greater sensitivity. Without the hot-mirror, the red, green and blue (or cyan, yellow and magenta) colored micro-filters placed over the sensor elements pass varying amounts of ultraviolet (blue window) and infrared (primarily red and somewhat lesser the green and blue micro-filters).


title: Photography

text: Uses of full spectrum photography are for fine art photography, geology, forensics and law enforcement.


title: Photography

text: Layering is a photographic composition technique that manipulates the foreground, subject or middle-ground, and background layers in a way that they all work together to tell a story through the image. Layers may be incorporated by altering the focal length, distorting the perspective by positioning the camera in a certain spot. People, movement, light and a variety of objects can be used in layering.


title: Photography

text: Digital methods of image capture and display processing have enabled the new technology of "light field photography" (also known as synthetic aperture photography). This process allows focusing at various depths of field to be selected "after" the photograph has been captured. As explained by Michael Faraday in 1846, the "light field" is understood as 5-dimensional, with each point in 3-D space having attributes of two more angles that define the direction of each ray passing through that point.


title: Photography

text: These additional vector attributes can be captured optically through the use of microlenses at each pixel point within the 2-dimensional image sensor. Every pixel of the final image is actually a selection from each sub-array located under each microlens, as identified by a post-image capture focus algorithm.


title: Photography

text: Besides the camera, other methods of forming images with light are available. For instance, a photocopy or xerography machine forms permanent images but uses the transfer of static electrical charges rather than photographic medium, hence the term electrophotography. Photograms are images produced by the shadows of objects cast on the photographic paper, without the use of a camera. Objects can also be placed directly on the glass of an image scanner to produce digital pictures.


title: Photography

text: Amateur photographers take photos for personal use, as a hobby or out of casual interest, rather than as a business or job. The quality of amateur work can be comparable to that of many professionals. Amateurs can fill a gap in subjects or topics that might not otherwise be photographed if they are not commercially useful or salable. Amateur photography grew during the late 19th century due to the popularization of the hand-held camera. Twenty-first century social media and near-ubiquitous camera phones have made photographic and video recording pervasive in everyday life. In the mid-2010s smartphone cameras added numerous automatic assistance features like color management, autofocus face detection and image stabilization that significantly decreased skill and effort needed to take high quality images.


title: Photography

text: Commercial photography is probably best defined as any photography for which the photographer is paid for images rather than works of art. In this light, money could be paid for the subject of the photograph or the photograph itself. Wholesale, retail, and professional uses of photography would fall under this definition. The commercial photographic world could include:


title: Photography

text: During the 20th century, both fine art photography and documentary photography became accepted by the English-speaking art world and the gallery system. In the United States, a handful of photographers, including Alfred Stieglitz, Edward Steichen, John Szarkowski, F. Holland Day, and Edward Weston, spent their lives advocating for photography as a fine art.


title: Photography

text: At first, fine art photographers tried to imitate painting styles. This movement is called Pictorialism, often using soft focus for a dreamy, 'romantic' look. In reaction to that, Weston, Ansel Adams, and others formed the Group f/64 to advocate 'straight photography', the photograph as a (sharply focused) thing in itself and not an imitation of something else.


title: Photography

text: The aesthetics of photography is a matter that continues to be discussed regularly, especially in artistic circles. Many artists argued that photography was the mechanical reproduction of an image. If photography is authentically art, then photography in the context of art would need redefinition, such as determining what component of a photograph makes it beautiful to the viewer. The controversy began with the earliest images "written with light"; Nicéphore Niépce, Louis Daguerre, and others among the very earliest photographers were met with acclaim, but some questioned if their work met the definitions and purposes of art.


title: Photography

text: Clive Bell in his classic essay "Art" states that only "significant form" can distinguish art from what is not art.


title: Photography

text: On 7 February 2007, Sotheby's London sold the 2001 photograph "99 Cent II Diptychon" for an unprecedented $3,346,456 to an anonymous bidder, making it the most expensive at the time.


title: Photography

text: Conceptual photography turns a concept or idea into a photograph. Even though what is depicted in the photographs are real objects, the subject is strictly abstract.


title: Photography

text: In parallel to this development, the then largely separate interface between painting and photography was closed in the early 1970s with the work of the photo artists Pierre Cordier (Chimigramm), Chemigram and Josef H. Neumann, Chemogram. In 1974 the chemograms by Josef H. Neumann concluded the separation of the painterly background and the photographic layer by showing the picture elements in a symbiosis that had never existed before, as an unmistakable unique specimen, in a simultaneous painterly and at the same time real photographic perspective, using lenses, within a photographic layer, united in colors and shapes. This Neumann chemogram from the seventies of the 20th century thus differs from the beginning of the previously created cameraless chemigrams of a Pierre Cordier and the photogram Man Ray or László Moholy-Nagy of the previous decades. These works of art were almost simultaneous with the invention of photography by various important artists who characterized Hippolyte Bayard, Thomas Wedgwood, William Henry Fox Talbot in their early stages, and later Man Ray and László Moholy-Nagy in the twenties and by the painter in the thirties Edmund Kesting and Christian Schad by draping objects directly onto appropriately sensitized photo paper and using a light source without a camera.


title: Photography

text: Photojournalism is a particular form of photography (the collecting, editing, and presenting of news material for publication or broadcast) that employs images in order to tell a news story. It is now usually understood to refer only to still images, but in some cases the term also refers to video used in broadcast journalism. Photojournalism is distinguished from other close branches of photography (e.g., documentary photography, social documentary photography, street photography or celebrity photography) by complying with a rigid ethical framework which demands that the work be both honest and impartial whilst telling the story in strictly journalistic terms. Photojournalists create pictures that contribute to the news media, and help communities connect with one other. Photojournalists must be well informed and knowledgeable about events happening right outside their door. They deliver news in a creative format that is not only informative, but also entertaining, including sports photography.


title: Photography

text: The camera has a long and distinguished history as a means of recording scientific phenomena from the first use by Daguerre and Fox-Talbot, such as astronomical events (eclipses for example), small creatures and plants when the camera was attached to the eyepiece of microscopes (in photomicroscopy) and for macro photography of larger specimens. The camera also proved useful in recording crime scenes and the scenes of accidents, such as the Wootton bridge collapse in 1861. The methods used in analysing photographs for use in legal cases are collectively known as forensic photography. Crime scene photos are taken from three vantage point. The vantage points are overview, mid-range, and close-up.


title: Photography

text: In 1845 Francis Ronalds, the Honorary Director of the Kew Observatory, invented the first successful camera to make continuous recordings of meteorological and geomagnetic parameters. Different machines produced 12- or 24- hour photographic traces of the minute-by-minute variations of atmospheric pressure, temperature, humidity, atmospheric electricity, and the three components of geomagnetic forces. The cameras were supplied to numerous observatories around the world and some remained in use until well into the 20th century. Charles Brooke a little later developed similar instruments for the Greenwich Observatory.


title: Photography

text: Science uses image technology that has derived from the design of the Pin Hole camera. X-ray machines are similar in design to Pin Hole cameras with high-grade filters and laser radiation.


title: Photography

text: Photography has become universal in recording events and data in science and engineering, and at crime scenes or accident scenes. The method has been much extended by using other wavelengths, such as infrared photography and ultraviolet photography, as well as spectroscopy. Those methods were first used in the Victorian era and improved much further since that time.


title: Photography

text: The first photographed atom was discovered in 2012 by physicists at Griffith University, Australia. They used an electric field to trap an "Ion" of the element, Ytterbium. The image was recorded on a CCD, an electronic photographic film.


title: Photography

text: Wildlife photography involves capturing images of various forms of wildlife. Unlike other forms of photography such as product or food photography, successful wildlife photography requires a photographer to choose the right place and right time when specific wildlife are present and active. It often requires great patience and considerable skill and command of the right photographic equipment.


title: Photography

text: There are many ongoing questions about different aspects of photography. In her "On Photography" (1977), Susan Sontag dismisses the objectivity of photography. This is a highly debated subject within the photographic community. Sontag argues, "To photograph is to appropriate the thing photographed. It means putting one's self into a certain relation to the world that feels like knowledge, and therefore like power." Photographers decide what to take a photo of, what elements to exclude and what angle to frame the photo, and these factors may reflect a particular socio-historical context. Along these lines, it can be argued that photography is a subjective form of representation.


title: Photography

text: Modern photography has raised a number of concerns on its effect on society. In Alfred Hitchcock's "Rear Window" (1954), the camera is presented as promoting voyeurism. 'Although the camera is an observation station, the act of photographing is more than passive observing'.


title: Photography

text: The camera doesn't rape or even possess, though it may presume, intrude, trespass, distort, exploit, and, at the farthest reach of metaphor, assassinate – all activities that, unlike the sexual push and shove, can be conducted from a distance, and with some detachment.


title: Photography

text: Digital imaging has raised ethical concerns because of the ease of manipulating digital photographs in post-processing. Many photojournalists have declared they will not crop their pictures or are forbidden from combining elements of multiple photos to make "photomontages", passing them as "real" photographs. Today's technology has made image editing relatively simple for even the novice photographer. However, recent changes of in-camera processing allow digital fingerprinting of photos to detect tampering for purposes of forensic photography.


title: Photography

text: Photography is one of the new media forms that changes perception and changes the structure of society. Further unease has been caused around cameras in regards to desensitization. Fears that disturbing or explicit images are widely accessible to children and society at large have been raised. Particularly, photos of war and pornography are causing a stir. Sontag is concerned that "to photograph is to turn people into objects that can be symbolically possessed". Desensitization discussion goes hand in hand with debates about censored images. Sontag writes of her concern that the ability to censor pictures means the photographer has the ability to construct reality.


title: Photography

text: One of the practices through which photography constitutes society is tourism. Tourism and photography combine to create a "tourist gaze"


title: Photography

text: in which local inhabitants are positioned and defined by the camera lens. However, it has also been argued that there exists a "reverse gaze" through which indigenous photographees can position the tourist photographer as a shallow consumer of images.


title: Photography

text: Photography is both restricted and protected by the law in many jurisdictions. Protection of photographs is typically achieved through the granting of copyright or moral rights to the photographer. In the United States, photography is protected as a First Amendment right and anyone is free to photograph anything seen in public spaces as long as it is in plain view. In the UK, a recent law (Counter-Terrorism Act 2008) increases the power of the police to prevent people, even press photographers, from taking pictures in public places. In South Africa, any person may photograph any other person, without their permission, in public spaces and the only specific restriction placed on what may not be photographed by government is related to anything classed as national security. Each country has different laws.


title: Refractive index

text: In optics, the refractive index (or refraction index) of an optical medium is a dimensionless number that gives the indication of the light bending ability of that medium.


title: Refractive index

text: The refractive index determines how much the path of light is bent, or refracted, when entering a material. This is described by Snell's law of refraction, , where "θ" and "θ" are the angle of incidence and angle of refraction, respectively, of a ray crossing the interface between two media with refractive indices "n" and "n". The refractive indices also determine the amount of light that is reflected when reaching the interface, as well as the critical angle for total internal reflection, their intensity (Fresnel's equations) and Brewster's angle.


title: Refractive index

text: The refractive index can be seen as the factor by which the speed and the wavelength of the radiation are reduced with respect to their vacuum values: the speed of light in a medium is , and similarly the wavelength in that medium is , where "λ" is the wavelength of that light in vacuum. This implies that vacuum has a refractive index of 1, and assumes that the frequency () of the wave is not affected by the refractive index.


title: Refractive index

text: The refractive index may vary with wavelength. This causes white light to split into constituent colors when refracted. This is called dispersion. This effect can be observed in prisms and rainbows, and as chromatic aberration in lenses. Light propagation in absorbing materials can be described using a complex-valued refractive index. The imaginary part then handles the attenuation, while the real part accounts for refraction. For most materials the refractive index changes with wavelength by several percent across the visible spectrum. Nevertheless, refractive indices for materials are commonly reported using a single value for "n", typically measured at 633 nm.


title: Refractive index

text: The concept of refractive index applies across the full electromagnetic spectrum, from X-rays to radio waves. It can also be applied to wave phenomena such as sound. In this case, the speed of sound is used instead of that of light, and a reference medium other than vacuum must be chosen.


title: Refractive index

text: For lenses (such as eye glasses), a lens made from a high refractive index material will be thinner, and hence lighter, than a conventional lens with a lower refractive index. Such lenses are generally more expensive to manufacture than conventional ones.


title: Refractive index

text: The relative refractive index of an optical medium 2 with respect to another "reference" medium 1 (n) is given by the ratio of speed of light in medium 1 to that in medium 2. This can be expressed as follows:


title: Refractive index

text: If the "reference" medium 1 is vacuum, then the refractive index of medium 2 is considered with respect to vacuum. It is simply represented as n and is called the absolute refractive index of medium 2.


title: Refractive index

text: The absolute refractive index "n" of an optical medium is defined as the ratio of the speed of light in vacuum, , and the phase velocity "v" of light in the medium,


title: Refractive index

text: The phase velocity is the speed at which the crests or the phase of the wave moves, which may be different from the group velocity, the speed at which the pulse of light or the envelope of the wave moves. Historically air at a standardized pressure and temperature has been common as a reference medium.


title: Refractive index

text: Thomas Young was presumably the person who first used, and invented, the name "index of refraction", in 1807.


title: Refractive index

text: At the same time he changed this value of refractive power into a single number, instead of the traditional ratio of two numbers. The ratio had the disadvantage of different appearances. Newton, who called it the "proportion of the sines of incidence and refraction", wrote it as a ratio of two numbers, like "529 to 396" (or "nearly 4 to 3"; for water). Hauksbee, who called it the "ratio of refraction", wrote it as a ratio with a fixed numerator, like "10000 to 7451.9" (for urine). Hutton wrote it as a ratio with a fixed denominator, like 1.3358 to 1 (water).


title: Refractive index

text: Young did not use a symbol for the index of refraction, in 1807. In the later years, others started using different symbols:


title: Refractive index

text: where "n" is the refractive index, λ is the wavelength, "A", "B", "C", etc., are coefficients that can be determined for a material by fitting the equation to measured refractive indices at known wavelengths. The coefficients are usually quoted for λ as the vacuum wavelength in micrometres.


title: Refractive index

text: For visible light most transparent media have refractive indices between 1 and 2. A few examples are given in the adjacent table. These values are measured at the yellow doublet D-line of sodium, with a wavelength of 589 nanometers, as is conventionally done. Gases at atmospheric pressure have refractive indices close to 1 because of their low density. Almost all solids and liquids have refractive indices above 1.3, with aerogel as the clear exception. Aerogel is a very low density solid that can be produced with refractive index in the range from 1.002 to 1.265. Moissanite lies at the other end of the range with a refractive index as high as 2.65. Most plastics have refractive indices in the range from 1.3 to 1.7, but some high-refractive-index polymers can have values as high as 1.76.