Friday, September 21, 2012

Depth of Field


Wednesday, September 19, 2012

Understanding F-Stop and Lens Speed

The photographer adjusts the opening of the aperture by setting the f-stop. An f-stop is a ratio of the focal length of the lens to the diameter of the opening of the aperture. For example, a 50 mm lens with an aperture opened up to a diameter of 12.5 mm results in an f-stop of f4 (50 ÷ 12.5 = 4).

Tuesday, September 18, 2012


The aperture is the opening in the lens (created by an adjustable iris or diaphragm) that allows light to pass through. The exposure of the image is determined by the combination of shutter speed and the opening of the aperture. The larger the aperture, the more light is allowed to pass through the lens. The aperture is measured in f-stops, and each stop represents a factor of two in the amount of light admitted. The aperture setting (f-stop), combined with the focal length of the lens, determines the depth of field of an image. For more information on depth of field.

Sunday, September 16, 2012

Understanding Digital Zoom

The digital zoom feature offered by some camera models does not really zoom in closer to the subject. Digital zoom crops into the center area of the captured frame, effectively enlarging the pixels. This results in a picture with a lower overall image quality. If you don’t have a telephoto or optical zoom lens and you want a close-up, physically move closer to the subject, if you can.

Thursday, September 13, 2012

Understanding Lens Multiplication with DSLRs

Most interchangeable lenses were originally created and rated for the 35 mm film plane of traditional SLRs. If you compare the area of a 35 mm film plane with the area of most digital image sensors’ image planes, you’ll see  that the area of most digital image sensors is a bit smaller. The focal length of a lens changes when it is put on a DSLR with a digital image sensor smaller than 35 mm. This smaller image plane effectively increases the focal length of the lens because more of the image circle coming out of the lens is cropped. For example, if you put a 100 mm lens on a DSLR that has a 24 mm digital image sensor, the focal length of the lens is multiplied by a factor of approximately 1.3. A 100 mm lens with a 1.3x multiplication factor effectively becomes a 130 mm lens (100 mm multiplied by 1.3). Another reason to take lens multiplication into account is that shooting wide-angle images becomes increasingly difficult when using cameras with smaller digital image sensors. For example, if your digital image sensor is 24 mm, you require a lens with a focal length less than 24 mm to achieve a wide-angle view. Check your camera specifications for the size of your digital image sensor.

Camera Components and Concepts - Lens

The basic components of a DSLR are described below. (Most of the components in a rangefinder are also found in a DSLR.)
Lens, Aperture, Shutter, Digital image sensor, Memory card, External flash

A lens is a series of sophisticated elements, usually glass, constructed to refract and focus the reflective light from a scene at a specific point—the digital image sensor.

Wednesday, September 12, 2012

Digital Point-and-Shoot

This is a lightweight digital camera, aptly named after the two steps required of the photographer to capture an image. Basically, point-and-shoot cameras require pointing the camera and taking the picture without manually adjusting settings such as the aperture, shutter speed, focus, and other settings that professional photographers routinely set on more sophisticated cameras.

Digital Single-Lens Reflex (DSLR)

This camera is named for the reflexing mirror that allows you to frame the image through the lens prior to capturing the image. As light passes through the DSLR camera’s lens, it falls onto a reflexing mirror and then passes through a prism to the viewfinder. The viewfinder image corresponds to the actual image area. When the picture is taken, the mirror reflexes, or moves up and out of the way, allowing the open shutter to expose the digital image sensor, which captures the image. Most features on a DSLR are adjustable, allowing for greater control over the captured image. Most DSLR cameras also allow the use of interchangeable lenses, meaning you can swap lenses of different  focal lengths on the same camera  body.
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