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[OM] Resolution for various SQF grades

Subject: [OM] Resolution for various SQF grades
From: Gary Reese <pcacala@xxxxxxxxxxxxx>
Date: Wed, 20 Dec 2000 10:57:40 -0800
I had a chance to examine through a Leitz microscope some lens test
slides in which I had resolution test charts in the center and corner.
Here is AN APPROXIMATE TRENDLINE guide to the average resolution in line
pairs per millimeter attained for various SQF grades on Fujichrome 64T
(original emulsion) film. Figures would be higher with slow B&W films,
so these aren't very comparable to lpm data on the WWW. Also, SQF grades
are also based on contrast, so resolution had quite a range within
grades.

Center:
A+ = 61+
A = 58
A- = 57
B+ = 54
B = 51
B- = 47
C+ = 45
C = <41

Corner:
A+ = 61+
A = 55
A- = 51
B+ = 49
B = 46
B- = 43
C+ = 41
C = <41

The highest resolution attained was a contrasty 78 lpm at f/8 through
f/22 in the center of the Nikon Nikkor 55mm f/2.8 AIS slides, with the
corner peaking at 65 lpm for f/8. The 50mm f/3.5 Zuiko at f/8 got 65 lpm
center and 57 lpm corner. One of Canon's sharpest lenses, the original
35mm f/2 "Concave," with a radioactive thorium floride element, got 73
lpm center and 57 lpm corner (better than the heralded 50mm f/1.4). I
didn't have a resolution chart in the 250mm f/2 Zuiko test, but looking
at fine details, the Zuiko at f/5.6 (optimum aperture) is contrastier
and of equal resolution to the Nikkor in the corners and a hair better
in the center. Considering that the 55mm Nikkor is recognized as one of
the highest performing 35mm SLR lenses in the world, it makes the rarely
tested 250mm Zuiko (an APO) look great.

I have a rather small selection of slides with resolution charts, so
there isn't much more I can say about comparisons, except that the
Tamron 80-200mm f/2.8 SP at its optimal focal length (80mm) and optimum
aperture (f/5.6) attained a kind of washed out 65 lpm center and 57 lpm
corner. Stated another way, it can resolve as well as the 50mm f/3.5
Zuiko, but can't attain the same level of contrast.

Gary Reese
Las Vegas, NV


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