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Chromatic Aberration -
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. ɡ Dispersion 7600 3900 .
, ( ) .
Chromatic aberration . Achromatic or apochromatic doublets .
. APO UD-SUD-CaF2-LD-SLD ED ɡ CaF2 Crystallizing calcium fluoride 1960 1970 Ultra-low dispersion UD 1990 Super UD glass EF lenses Nikon ED-Extra-low dispersion. .