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The most common application for this is the treatment of strabismus. By moving the image in front of the deviated eye, double vision can be avoided and comfortable binocular vision can be achieved. Other applications include yoked prism where the image is shifted an equal amount in each eye.
In photography, distortion is particularly associated with zoom lenses, particularly large-range zooms, but may also be found in prime lenses, and depends on focal distance – for example, the Canon EF 50mm f / 1.4 exhibits barrel distortion at extremely short focal distances.
In some circumstances, it is possible to correct some of the effects of chromatic aberration in digital post-processing. However, in real-world circumstances, chromatic aberration results in permanent loss of some image detail. Detailed knowledge of the optical system used to produce the image can allow for some useful correction.
Rectaflex, the first pentaprism SLR for eye-level viewing. The historic East Germany Contax S, the second pentaprism SLR for eye-level viewing. A perspective drawing showing how a pentaprism corrects a laterally reversed SLR image. Asahiflex — the first single-lens reflex camera made in Japan.
The optical quality of the eye is limited by optical aberrations, diffraction and scatter. [1] Correction of spherocylindrical refractive errors has been possible for nearly two centuries following Airy's development of methods to measure and correct ocular astigmatism.
The Catadioptric system, where a spherical reflector is combined with a lens with the opposite spherical aberration, corrects the common optical errors of a reflector such as the Cassegrain system, making it suitable for devices that need a large aberration free focal plane (cameras).
Compression distortion is most familiar in looking through binoculars or telescopes, as in telescopic sights, while a similar effect is seen in fixed-slit strip photography, notably a photo finish, where all capture is parallel to the capture, completely eliminating perspective (a side view).
Tilt-lens photo of a model train. Note how the focus plane is along the train, and how the blurring of the background proceeds from left to right. Tilt–shift photography is the use of camera movements that change the orientation or position of the lens with respect to the film or image sensor on cameras .
There are two distinct forms of astigmatism. The first is a third-order aberration, which occurs for objects (or parts of objects) away from the optical axis. This form of aberration occurs even when the optical system is perfectly symmetrical.
Flat-field correction (FFC) is a digital imaging technique to mitigate the image detector pixel-to-pixel sensitivity and distortions in the optical path. It is a standard calibration procedure in everything from personal digital cameras to large telescopes.