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In optics, chromatic aberration (CA), also called chromatic distortion, color aberration, color fringing, or purple fringing, is a failure of a lens to focus all colors to the same point. [ 1 ] [ 2 ] It is caused by dispersion : the refractive index of the lens elements varies with the wavelength of light .
1: Imaging by a lens with chromatic aberration. 2: A lens with less chromatic aberration. In optics, aberration is a property of optical systems, such as lenses and mirrors, that causes the image created by the optical system to not be a faithful reproduction of the object being observed.
System sharpness is affected by the lens (design and manufacturing quality, focal length, aperture, and distance from the image center) and sensor (pixel count and anti-aliasing filter). In the field, sharpness is affected by camera shake (a good tripod can be helpful), focus accuracy, and atmospheric disturbances (thermal effects and aerosols).
The DXOMARK Lens Score provides ratings for camera lenses, as tested using its proprietary tool-set in combination with various camera models. [8] [10] [17] As with the DxOMark Sensor Score, the DXOMARK Lens Score is an aggregation of five separate sub-scores; namely: sharpness, distortion, vignetting, transmission, and chromatic aberration.
Criteria relating CoC to the lens focal length have also been used. Kodak recommended 2 minutes of arc (the Snellen criterion of 30 cycles/degree for normal vision) for critical viewing, yielding a CoC of about f /1720, where f is the lens focal length. [8] For a 50 mm lens on full-frame 35 mm format, the corresponding CoC is 0.0291 mm.
The ability of a lens to resolve detail is usually determined by the quality of the lens, but is ultimately limited by diffraction.Light coming from a point source in the object diffracts through the lens aperture such that it forms a diffraction pattern in the image, which has a central spot and surrounding bright rings, separated by dark nulls; this pattern is known as an Airy pattern, and ...
A person's visual acuity is registered documenting the following: whether the test was for distant or near vision, the eye(s) evaluated and whether corrective lenses (i.e. glasses or contact lenses) were used: Distance from the chart D (distant) for the evaluation done at 20 feet (6 m). N (near) for the evaluation done at 15.7 inches (400 mm).
This means the lens's F-number value is fixed to the overall designed focal ratio of the optical system (the diameter of the primary mirror divided into the focal length). The inability to stop down the lens results in the catadioptric lens having a short depth of field.
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