Erwin Voogt writes:
> This brings me to another thing that amazes me: why not use a flash to
> eliminate all vibrations? My own tests using Kodachrome 25 and a flash
You should feel free to test all the Zuikos this way. There are
different ways to skin the cat. But, the relevance question will arise.
How many of us actually shoot day in and day out with Kodachrome 25? Is
flash photography the predominant way we shoot? Caution: Kodachrome 25
stocks might run out before you complete testing all lenses and their
variations.
> showed that at F5.6 all my lenses reach the sharpness of the grain of
the
> K25, at the corner of the images. It was simply not possible for me to
> notice an increase in sharpness from that point with all my lenses
(primes
> and zooms).
Perhaps you need a finer detailed evaluation point? A resolution test
chart going into the range of 200 lp/mm will certainly peter out at
around 100 lp/mm with most any 35mm lens and color films in the ISO
25-100 range.
> I used a Leitz Colorplan 90/2.5 to project the images on a
> smooth white screen. You need this to see the extremely fine grain of
the
> K25.
I'm not impressed with the corner resolution of that projector lens,
although contrast center and corner is dandy. Perhaps the curved field
version is better, or the super or pro versions of the Colorplan. So
far, a blue lettering Kodak Ektanar C 102mm f/2.8 is the best bang for
the buck in my early stage of comparisons. I really don't want to start
an off topic discussion of this, though.
> - On a commercial film even cheap lenses should reach an A+ level at
F5.6
Depends on where you set your baseline standard. Early on I set SQF=A+
to be what I saw through a 50mm f/2 Macro Zuiko/OM-1 combo at optimum
aperture. It was a good choice. It took awhile to find some lenses
that would outperform it at certain apertures, but the improvement isn't
significant at the 24x magnification to which I made the SQF
evaluations. I can see it at 100x using my pocket microscope. Barely so
on Fujichrome 64T Type I film and, now, more dramatically on the newer
Type II film. Which is another way of saying that an A+ level exists in
my head only and only for the combination of the projector lens I used,
the film I used and the 24x reproduction magnification I used.
> - Lower ratings at F5.6 - F11 must be caused by external factors.
> - Since the SQF rating shows many B's at F8, the influence of external
> factors
> in the tests is in my opinion very large.
Real world picture taking is full of so many "external factors" that it
is a minor miracle everytime we get a keeper shot. MTF graphs are so far
removed from the external factors that effect each and every one of our
shots that it amazes me so much attention is being paid to them.
Gary Reese
Las Vegas, NV
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