NSL Photography's™ Glossary of Photographic Terms - I

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Image Stabilization (Vibration Reduction)
With still cameras, camera shake is particularly problematic at slow shutter speeds or with long focal length (telephoto) lenses. Image stabilization (vibration reduction) is a mechanism used in a camera that stabilizes the recorded image by varying the optical path to the sensor. Stabilization for SLR and DSLR cameras is usually performed by the lens. Many digital point and shoot cameras also have image stabilization, but performed in the camera itself.

Image stabilization can often permit the use of shutter speeds 2–4 stops slower (exposures 4–16 times longer) than a person can normally accomplish hand holding a camera, for any particular lens/camera combination, although even slower effective speeds have been reported.

Some image stabilized lenses have an "Active Mode" intended to be used when shooting from a moving vehicle, such as a car or boat, to correct for larger shakes than the "Normal Mode."

Incident Light
Light falling on a surface as opposed to the light reflected by it.

Infinity
Infinite distance. In practice, a distance so great that any object at that distance will be reproduced sharply if the lens is set at its infinity position, one focal length from the film.

Interchangeable Lens
Lens designed to be readily attached to and detached from a camera.

Interpolation
Interpolation (sometimes called resampling) is a method to increase or decrease the number of pixels in a digital image. Some digital cameras use interpolation to produce a larger image than the sensor captured to create digital zoom. Virtually all image editing software support one or more methods of interpolation. How smoothly images are enlarged without introducing jagged edges, or lack of focus sharpness depends on the sophistication of the algorithm.

Inverted Telephoto Lens
Lens constructed so that the back focus (distance from rear of lens to film) is greater than the focal length of the lens. This construction allows room for mirror movement when short focus lenses are fitted to SLR or DSLR cameras.

IPTC (International Press Telecommunications Council
The IPTC, based in London, UK, is a consortium of the world's major news agencies, news publishers and news industry vendors. It develops and maintains technical standards for improved news exchange that are used by virtually every major news organization in the world.

The standards, codes and fields of the IPTC permit photographers to describe their work in a uniform way understood by news companies and publishers across the globe and within major software used by photographers such as Adobe Photoshop, Adobe Lightroom, Microsoft Expression Media, and Photo Mechanic. It also enables photographers to properly identify themselves and their work as per the Digital Millennium Copyright Act (DMCA), and general US copyright law.

Use of controlled vocabulary within IPTC data fields permits keyword and terms consistency among photographers regardless of location.

Iris
Strictly, iris diaphragm the device consisting of thin overlapping metal leaves pivoting outwards to form a circular opening of variable size to control light transmission through a lens.

ISO Speed
The international standard for representing film and sensor sensitivity. The ISO speed is the emulsion speed (sensitivity) of the film or the sensitivity of the sensor as determined by the standards of the International Standards Organization. In these standards, both arithmetic (ASA) and logarithmic (DIN) speed values are expressed in a single ISO term.

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