Chromatic Aberration in Camera Lenses
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What is chromatic aberration
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When you are focusing an image it
sometimes happens that rainbow like colors appear, fringing the edges
of the subject. This defect is called chromatic, or color, aberration,
and is an effect visually similar to the spreading of white light into
its spectral components by a prism. It takes two forms: lateral and
longitudinal.
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Why chromatic aberration happens
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Lateral chromatic aberration occurs when
different colors of light (that is, light of differing wavelengths)
form images of different sizes. Longitudinal aberration occurs when
different colors of light come to a focus at different distances from
the lens.
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How to overcome chromatic aberration
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Chromatic aberration is a basic lens
fault that cannot be corrected by closing the lens aperture. In
black-and-white photography, however, where the effect is to blur the
image, you can increase the image sharpness by using color filters to
absorb one or more of the color fringes, focusing with the filter in
place (only when the filter is in place can you tell when a true focus
is achieved, because otherwise all you see, at best, is an un-sharp
image).
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