Värivirhettä

Värivirhettä refers to color aberration, an optical phenomenon that occurs when a lens fails to focus all colors of light at the same point. This can result in visible colored fringes or halos around objects, particularly noticeable at high contrast edges. There are two main types: longitudinal chromatic aberration and lateral chromatic aberration. Longitudinal chromatic aberration causes different wavelengths of light to be focused at different distances from the lens, leading to a general fuzziness and color fringing that can vary with focus distance. Lateral chromatic aberration, on the other hand, causes different wavelengths to be magnified differently, resulting in color fringing that is more pronounced towards the edges of the image.

This optical distortion is a common issue in simpler lens designs or when using lenses at their widest apertures. It is caused by the variation in the refractive index of glass with wavelength, a property known as dispersion. While often considered an undesirable artifact, in some artistic contexts, a slight amount of chromatic aberration can be intentionally introduced or accepted for its aesthetic effect. Lens manufacturers employ various techniques to minimize värivirhettä, such as using multiple lens elements made from different types of glass with complementary dispersive properties (achromatic or apochromatic lenses). Digital image processing also offers tools to correct or reduce the appearance of color aberration in photographs.