Chromatic Aberration
An optical distortion in lenses caused by material dispersion, where different wavelengths of light focus at different spatial positions.
Governing formula
f_blue < f_red (v = c/n(λ))
SI unit
m
In depth
Glass refracts blue light more strongly than red light, focusing blue closer to the lens than red. Corrected using achromatic doublets combining crown and flint glass.
Examples in the real world
Color fringing (purple or magenta halos) visible around high-contrast edges in cheap camera lenses.