Clyde S. writes:
<< Gary, how are you testing for color fringing? I seem to recall Bob
Atkins(?) accused the 350/2.8 of aberrations also, though at the time I
wondered if it was just his sample. >>
At 100x magnification I look for prismatic-like separation of the colors
making up a black line near the edges of the frame. Often you will
double triple lines slightly offset from each other: a yellow to one
side and a blue to the other, with a no longer pure black in between.
The 350mm f/2.8 isn't an apo lens, so it WILL show color fringing, which
is chromatic aberration (not spherical like crept into my last posting).
My 350mm test slides aren't labled, so they are particularily hard to
find amount the 4 huge binder of test slides. Someday I'll stumble on
them and will report back on color fringing. But any owner can look at
their slides for evidence of the same. Lenses of 300mm and longer, as
well as fast designs of 180-300mm will readily show this aberration,
unless they are an apochromatically corrected design.
Gary
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