Citat:
Chromatic aberration
Chromatic aberration occurs due to the variation of refractive index with wavelength for a lens material (there is no chromatic aberation in curved mirrors). This wavelength dependence results in slightly different focal lengths for different wavelengths of light. Compound lenses, called achromats, can reduce or eliminate chromatic aberation because the components are chosen such that the variation in refractive index as a function of wavelength cancels out.
Laicki receno, kod sociva kojima fokus zavisi od boje dolazi do pojave "duhova" u drugoj boji, obicno ljubicastoj ili zelenoj. Ovo se najcesce primeti kod objektiva sa velikim povecanjem na mestime gde je veliki kontrast na fotografiji. Karakteristican slucaj je, recimo, kada slikas krosnju drveta kroz koju se vidi nebo. Sve hromatske aberacije koje sam video na digitalnim fotoaparatima bile su ljubicaste.