An achromatic lens or achromat is a lens that is designed to limit the effects of chromatic aberration.

Chromatic aberration is caused by a lens having a different refractive index for different wavelengths of light. Chromatic aberration of a lens is seen as "fringes" of color around the image, because each color in the optical spectrum cannot be focused at a single common point on the optical axis. This effect is usually found in cheaper, single lens optics. To reduce this less than desireable effect, an achromatic lens is used in place of the single element lens.

Achromatic lenses are composed of two individual lenses made from glasses with different amounts of dispersion. One element is a concave lens made out of flint glass, which has relatively high dispersion, while the other, convex, element is made of crown glass, which has lower dispersion. The lens elements are mounted next to each other and shaped so that the chromatic aberration of one is counterbalanced by the chromatic aberration of the other. Together they form a lens that will bring two different wavelengths of light into a common focus on the same plane.

All of our 35mm lens adapters offered here are built with high grade achromatic lenses.

*Source: Wikipedia