NSL Photography's™ Glossary of Photographic Terms - V

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Variable Focus Lens
Lens of which the focal length can be continuously varied between set limits. The lens must be refocused with each change in focal length.

Vibration Reduction (Image Stabilization)
With still cameras, camera shake is particularly problematic at slow shutter speeds or with long focal length (telephoto) lenses. Vibration reduction (image stabilization) 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."

Device or system indicating the field of view encompassed by the camera lens. The term is sometimes used as a description of the type of camera that does not use reflex or "straight-through" viewing systems and therefore has to have a separate viewfinder.

Underexposure of image corners produced deliberately by shading or unintentionally by inappropriate equipment, such as unsuitable lens hood or badly designed lens. A common fault of wide-angle lenses, owing to reflection cut-off, etc. of some of the very oblique rays.

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