Definition of "achromatism" []

• The state or quality of being achromatic; as, the achromatism of a lens; achromaticity. (noun)
• The state of being free of colors, not emitting or separating into colors. (noun)
• Achromatopia. (noun)

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• "Very occasionally a person lacks all color-receptors and is completely color-blind, a condition called achromatism (ay-kroh'muh-tiz-um; "no color" G)."
• "Although this peculiar disharmony in the dispersive powers of the two glasses, crown and flint, was discovered almost immediately after achromatism was invented, it was only recently that the first successful attempts were made to produce different glasses, which, possessing the other requirements for achromatic objectives, would produce coincident spectra, or nearer so than the ordinary crown and flint glass do."
• "This increase is due in part to the diffraction of the telescope, to imperfect achromatism or spherical aberration of the objective, to irregular grinding of the glass, and especially to variations in the refraction of the air, which produce an oscillation of the image around a mean position."