A lens aberration is an optical flaw that stops a lens from forming a perfect image. Light from one point of the subject does not meet at exactly one point on the sensor or film, so the image can be soft, show color fringes or look distorted.
Common types include spherical aberration, chromatic aberration, coma, astigmatism, field curvature and distortion. Lens designers reduce them with several glass elements, special glass and aspherical lenses. Stopping down the aperture also reduces some aberrations.
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