At f22 you are at least partly testing which lens is least affected by
difffraction at small apertures. Likely the one with the physically
largest opening at f22 will perform the best. This isn't a good overall
test of lens quality. If you look at Gary's tests of the 35-70/3.6, you
will see that sharpness declines after f11. The tests of the 75-150/4
and 135/2.8 also show deterioration at f22. There are also several
comments about lower contrast (which affects perception of sharpness) at
f22.
Also, on a more general note, the emulsions on photo paper aren't
designed for very high resolution. It requires a print much larger than
4x6 to approach the resolving power of a good quality 35mm lens.
Automated photo processing/printing equipment for consumer 4x6 prints is
not designed for critical print to print sharpness either.
I'm not trying to say that the Vivitar isn't a good lens. I wouldn't be
at all surprised if it is and is likely better than the 75-150. I'm only
commenting that your testing metholodogy leaves a lot to be desired.
When you do more testing, try slide film and a powerful loupe or modest
power microscope. Testing at maximum and minimum apertures doesn't say
much about the f5.6-11 range where most 35mm lenses perform best. With
modest aperture zooms, f11 is a good place to test.
Moose
Benson Honig wrote:
I just tested a vivitar 80-200 (not a series one) against my 35-70 zuiko
3.5-4.5 , 135mm Zuiko f2.8, and my Zuiko 75-150 F4.
I compared approx. the same ranges (70 vs. 80 vs. 80 vs 135, vs. 135, 135)
all at F22. I found the vivitar surprisingly good. Under a magnifying
glass, it performed very nearly as good as the 35-70, and 135 2.8 and
actually somewhat better than the 75-150. All tripod shots, 250 sec, and
small f.stop, so these were
ideal conditions. The contrast on the vivitar was quite comparable. In sum,
without an extremely careful look under a strong magnifying glass at the
smallest details, differences between the lenses were not visible on a
standard 4x6 print, and even with a glass, barely so. This particular
Vivitar appears to be all metal construction. It says "image by vivitar,
80\200 1:4.5 mc macro focusing zoom and is a one touch. This lens is about
the same size and weight as the 75-150 F4, and seems to be all metal
construction. If it had not done so well, it was destined for the evil one,
but given that it is multicoat, and has a good range and weight, it has now
earned a place in the bag. Sometime later, I'll do another test for max.
f.stop, but since I plan to use it outdoors, probably on a tripod, stopping
down may not be such a big issue.
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