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Compression, long-lens, or telephoto distortion can be seen in images shot from a distance using a long focus lens or the more common telephoto sub-type (with an angle of view narrower than a normal lens). Distant objects look approximately the same size – closer objects are abnormally small, and more distant objects are abnormally large, and ...
In geometric optics, distortion is a deviation from rectilinear projection; a projection in which straight lines in a scene remain straight in an image.It is a form of optical aberration that may be distinguished from other aberrations such as spherical aberration, coma, chromatic aberration, field curvature, and astigmatism in a sense that these impact the image sharpness without changing an ...
Compression artifacts in compressed audio typically show up as ringing, pre-echo, "birdie artifacts", drop-outs, rattling, warbling, metallic ringing, an underwater feeling, hissing, or "graininess". An example of compression artifacts in audio is applause in a relatively highly compressed audio file (e.g. 96 kbit/sec MP3).
However telephoto designs increase the number of lens elements and can introduce flare and exacerbate some optical aberrations. Catadioptric lens - catadioptric lenses are a form of telephoto lens but with a light path that doubles back on itself and with an objective that is a mirror combined with some form of aberration correcting lens (a ...
The term telephoto ratio refers to the physical length of a lens divided by its focal length; where long-focus lenses have a telephoto ratio around 1, telephoto lenses have a ratio less than 1. As an example, one modern lens ( Canon EF 400 mm f /4 DO IS ) achieves a telephoto ratio of 0.58 in part due to a front (converging) lens group which ...
When still life scenes are stereographed, an ordinary single lens camera can be moved using a slide bar or similar method to generate a stereo pair. Multiple views can be taken and the best pair selected for the desired viewing method. For moving objects, a more sophisticated approach is used.
The zoom lens evolved from the focal length compression elements found in telephoto lens. [citation needed] Varying the spacing between a telephoto's front positive and rear negative cells changes the lens' magnification. However, this will upset focus and aberration optimization, and introduce pincushion distortion.
The human visual system model can produce desired effects in perception and vision. Examples of using an HVS model include color television, lossy compression, and Cathode-ray tube (CRT) television. Originally, it was thought that color television required too high a bandwidth for the then available technology.