Sunday, August 29, 2010

Color Calibration of Satellite Cameras

For those of you who do not know me, my name is Paul Matheson. I work with Nathan and Giordano at HP Labs. My background is in commercial print and I consider myself to be a printer. Hopefully I will be able to add something of value to this hallowed blog - if not, I am sure Nathan and Giordano will make me pay for several rounds at the Nuthouse so at least they'll get something of value out of me.
Several days ago I stumbled across this article explaining how satellite cameras are calibrated. It reminded me of Nathan's post about a revolutionary white reflectance standard for metrology - curiously enough, the post was entitled "Revolutionary White Reflectance Standard for Metrology." The original blog post is gone but I was able to find a couple of links to the blog, one of which included some of the text.
Unlike Nathan's post, Lake Tuz really is used for calibration. I knew that many satellites have cameras, but it never occurred to me that they would need calibrating or that image sensors in orbit degrade significantly. The thing that I enjoy most about this article is the fact that some smart person(s) figured out how to use unique geographic features as reflectance standards.
Science is cool.

Image of Lake Tuz from the Image Science and Analysis Laboratory, NASA-Johnson Space Center. "The Gateway to Astronaut Photography of Earth."

Friday, August 27, 2010

Is teamwork good or bad?

Actually, in today's issue the Science magazine editors phrased it differently:
"Two Heads Are Better Than One," but then you have to watch for the caveat. They summarize the research conducted in London and Aarhus as follows: "When two people peer into the distance and try to figure out if a faint number is a three or an eight, classical signal detection theory states that the joint decision can only be as good as that of the person with higher visual acuity. Bahrami et al. propose that a discussion not only of what each person perceives but also of the degree of confidence in those assignments can improve the overall sensitivity of the decision. Using a traditional contrast-detection task, they showed that, when the individuals did not differ too much in their powers of visual discrimination, collective decision-making significantly improved sensitivity. The model offered here formalizes debates held since the Enlightenment about whether collective thinking can outperform that of elite individuals."

Six vertically oriented Gabor patches displayed equidistantly around an imaginary circle

In their paper Optimally Interacting Minds in Science of 27 August 2010, the authors describe their experiment, in which six vertically oriented Gabor patches were displayed equidistantly around an imaginary circle. There was one oddball target that had slightly higher contrast than all of the others. Then they tested four models for a dyade identifying correctly the oddball patch.

The four models made different predictions for the relation between the slope of the psychometric function for each individual and the collective dyad; thus, by comparing predicted and observed dyad slopes, the researchers could distinguish the models:

  • CF: the joint decision is no better than a coin flip
  • BF: pairs of individuals learn, from trial-to-trial feedback, which of them is more accurate, so they eventually use that individual’s decisions
  • WCS: confidence, which they define as an internal estimate of the probability of being correct, is communicated
  • DSS: the mean and standard deviation of the sensory response to the stimulus about which the decision is made are communicated

The result is that when dyads have matching standard deviations, the DSS model is a better predictor, while when the standard deviations are different, the WCS model sets a quantitative limit on the usefulness of cooperation, so individuals with very different sensitivities are best advised to avoid collaboration and instead should rely entirely on the more sensitive individual.

Therefore, if you manage a team of color scientists, your encouragement of teamwork should depend on your management style.

If your style is the old guerilla approach, where a team of highly motivated researchers attack a hard problem, then you probably groom them at the same level and they will have matching standard deviations in their decisions. In this case, you will get much higher performance with teamwork.

If your style is the army approach, where a hierarchical team slugs away at a big project, teams can cooperate positively on small decisions, while important decisions are better made individually by the manager.

Finally, in the contemporary totem pole approach, where the crew is sorted by contribution to the bottom line and through the use of performance boni there is a large salary span, you are better off using the old divide and conquer management strategy and discourage team work: the member higher up un the totem pole rules the member below.

In summary, when the individuals do not differ too much in their powers of visual discrimination, collective decision-making significantly improves sensitivity, and this is also the caveat.

Saturday, August 21, 2010

Like being there in Hi-rez and Color

  1. Cincinnati waterfront captured on daguerreotype plates c.1848. Restored by conservators at George Eastman House in Rochester, New York. What was unexpected is the resolution of these daguerreotypes. The panoramic set could be blown up to 170 by 20 feet without losing clarity—a digital camera would require 140,000 megapixels per frame to match it. Since the exposure time was on the order of minutes, anything that moved significantly was not imaged. Particularly interesting is seeking out the "ghosts" of slower moving people and horse-drawn buggies moving along the line of sight of the camera.
  2. Photographic survey of the Russian Empire c.1910. Taken by Sergei Mikhailovich Prokudin-Gorskii under the auspices of Tsar Nicholas II before the outbreak of WW1 and the Russian Revolution. This is not (Ted) Turnerization of black and white photographs but a "digichromatographic" restoration of the original color plates. I highly recommend comparing with the more recent photographic views available in the accompanying Google Map links.

Tuesday, August 17, 2010

Glad not to be on the stake

Last month President Nicolas Sarkozy of France, addressing the International Conference on High Energy Physics in Paris, declared (click on "more" for official translations):

Certainement on ne peut qu'être saisi de vertige lorsqu'on essaie seulement d'imaginer les questions auxquelles vous vous attaquez ! Il fut un temps où elles relevaient de la métaphysique. Elle nous semble loin cette époque où les découvertes de Giordano Bruno lui valurent le bûcher et celles de Galilée, — mieux traité !— la prison. Estimez-vous heureux de vivre à votre époque ! La science est une démarche, je le sais, fragile et vous devez être défendus, vous les scientifiques, vous devez être défendus contre l'obscurantisme, contre le fanatisme, contre le refus des faits et contre le mépris de la vérité. Ces risques sont actuels, ils sont de tous temps et de toutes époques.


La science est un édifice qui doit être complet : il n'y a pas d'applications sans recherche fondamentale, il n'y a pas de saut qualitatif dans le progrès des connaissances en dehors de la recherche fondamentale et de ses découvertes. Ce n'est pas en prétendant améliorer la bougie qu'on a découvert l'électricité.

President Sarkozy addressing ICHEP2010

Official translation of the above citations:

The mind boggles at an attempt to even imagine the questions you explore. At one time these questions belonged to the realm of metaphysics. The days when Giordano Bruno was sent to the stake and Galileo (who received better treatment) to prison for their discoveries are long gone and you have the good fortune to live in our times. But science is, I am well aware, a fragile enterprise and scientists must be defended against obscurantism, fanaticism, wilful ignorance and contempt for the truth. These dangers still threaten us, as they always have.

The scientific edifice must be comprehensive: there can be no applications without basic research or breakthroughs without its results. Electricity was not discovered by attempting to improve the candle.

These are not just words. President Sarkozy announced France's plan to increase spending on higher education and basic & applied research by €35 billion for the next 4 years as part of the country's bailout strategy.

Friday, August 6, 2010

CPS: what are they?

To scientists formed throughout the Cold War, the term cybernetics leaves a funny taste in the mouth. During the Cold War, the West had astronauts while Eastern Europe had cosmonauts, and we had computer science while they had cybernetics. The term—from Greek kubernētēs ‘steersman,’ from kubernan ‘to steer’—used in this context goes back to 1948, when the American mathematician Norbert Wiener published the book Cybernetics or Control and Communication in the Animal and the Machine.