FWIW, I've also noticed a reduction in apparent chromatic aberration by
stopping down using a Vivitar T-mount preset 300/5.6 lens. Even with the
addition of a Kiron 1.4x teleconverter there was less chromatic aberration
when the lens was stopped down. This was observed in photos of this
weekend's 3/4 moon.
Beyond this I'm fairly ignorant of lens faults. My copy of "The Manual of
Photography (7th Ed.)" distinguishes between "axial chromatic aberration"
(commonly referred to as chromatic aberration) and "transverse chromatic
aberration" (commonly referred to as lateral color). While the first may be
minimized by stopping down, the latter (lateral color) is not corrected by
stopping down. And various apochromatic optical formulas are designed to
correct the former, while various extra low dispersion formulas (including
flourite) are designed to correct the latter.
That's just a rough summary of my understanding of what the book's editors
say.
It sounds to me as tho' what we're observing in the Zuiko 180/2.8 is
actually lateral color rather than axial chromatic aberration, according to
the Manual. But I could be misunderstanding the book. It says lateral
color error affects the edges of the image field (presumably the margins of
the negative or chrome). Does this mean the color fringing seen in specular
highlights and similarly bright areas elsewhere in the image are *not*
lateral color error, but are axial chromatic aberration? Because the Manual
states that all optical errors other than lateral color and diffraction can
be minimized by stopping down.
I dunno. Anybody else understand this subject better than I?
Lex
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