Re: Is it freaking Canon Day or something?

RichA wrote:
"Spherochromatism. A combination of spherical aberration and chromatic

aberration. Canon lenses (some of them) seem like teaching aids to
study optical aberrations.
http://www.vanwalree.com/optics/spherical.html "

Its better to call spherochromatism a variation of spherical aberration
with wavelength. Saying "a combination of spherical aberration and
chromatic aberration" sounds like spherical plus axial chromatic, which
is definitely not spherochromatism.

In photographic lenses it tends to be unimportant, but is occasionally
visible in defocused highlights and in extremely fast lenses used
wide-open. It only becomes a really big deal with certain types of
telescope objectives. For example, in Schmidt cameras and
Schmidt-Cassegrain telescopes spherochromatism is often the dominant
residual aberration.

.

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