Hi Windsor:
<< If macro correction is a large issue in a lens to be used for
macrophotography, why isn't it an issue when using a lens with macro
correction at "normal" shooting distances? >>
A lot has to do with the magnification ratio. First off, many general purpose
macros without floating elements are optimized for about 1:10 They fall-off
from prime performance towards infinity and towards 1:2 Olympus found a way
to boost performance above and below 1:10 by using floating elements AND
managed to give us an f/2.0 aperture in the process!
The 80 mm f/4.0 Zuikos aren't floating element designs. They are optimized
for 1:1 and not recommended outside the range of 2:1 to 1:2 1:1 requires a
symetrical or near symetrical optical construction incompatible with lenses
that focus to infinity or those used a high magnification ratios.
The 38 and 20 mm Macro Zuikos are reversed lenses (smallest elements forward),
which best suit high magnification ratios.
The 135 mm f/4.5 Macro Zuiko is optimized for 1:5 (if memory serves me right).
While it can focus to infinity, it's performance at that distance isn't very
good - IMHO. So, performance degradation at infinity should be an issue here.
Finally, someone might still want to know why most macro lens without floating
elements can still rate high at infinity. I guess I don't fully know, but
would guess that it is due to them having:
1) conservative designs with smaller maximum apertures
2) conservative ranges with maximum reproduction rations of 1:2 (less
extension tubes which DO degrade performance)
3) an optically most easy to correct range of 50-100 mm.
Gary Reese
Las Vegas, NV
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