Coma
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Coma
A lens aberration producing asymmetrical distortion of points in the image.
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Coma One of Seidel's five aberrations. The image of a point source of light is prevented from being brought into focus, but instead appears shaped as a comet or teardrop. Coma can be reduced by stopping down the lens.
Coma
A lens defect which results in points of light appearing in the image not as points but as discs with comet-like tails.
Coma
A lens aberration restricted to off axis image points; the inability of a lens to render point sources of light near the edges of the frame as circular; ...
Coma - the image of a point source of light cannot be brought into focus, but has instead a comet shape
Curvilinear distortion - distortion consisting of curved lines
Field curvature - the image is incorrectly curved ...
Coma This refers to the blurring of objects at the edge of the field of view, most common in short focal ratio Newtonian telescopes (at f/10 and longer, Newtonians are very well corrected for coma).
April 9 - Israeli Prime Minister Ariel Sharon is removed from office after four months in a coma.
April 9 - Hungarian parliamentary election, 2006
April 10 - Romano Prodi narrowly defeats Silvio Berlusconi in the Italian parliamentary elections.
However, just so you know what these lens aberrations are, a brief definition is provided for each of them in the glossary; they are as follows: Astigmatism Chromatic aberration Coma Curvilinear distortion Spherical aberration Today's lenses can ...
There are 3 aberrations which directly lower the sharpness of an image, Spherical Aberration, Astigmatism and Coma. Some lenses use aspheric elements to better correct spherical aberration at wide apertures.
This effect is achieved by choosing a relatively long exposure time and zooming just after the shutter is released. The picture below shows a sort of coma effect because the zooming was finished well before the shutter was closed.
Unless it’s blatantly obvious, I don’t comment much about vignetting, chromatic aberrations, coma, and other things that consume some reviewers. The final criterion is does the lens provide the results I desire?
 See also: Light, Aberration, Film, Photograph, Image
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