About a month ago I decided to burn up the three remaining rolls of
Kodachrome 25 in my freezer by performing a series of comparative lens
tests. The methodology was simple I imported text into Excel, repeated it
line after line with each line getting progressively smaller. This was
printed at 720 dpi on photo quality ink jet paper. The chart has text from
10 pts to 2 pts in size. I then took photos of the chart at various
aperture settings. The camera used was a PZ-1p, mounted on a Bogen 3036
tripo with a 3038 ball head. The idea was to get a relative comparison of
the performance of the lenses, not to measure them against an external
standard (like an LPM test.)
Two of the three rolls came back today, and here's the first set of results
comparing the Rikenon 55mm f1.2 to the A 50mm f1.4. Basically, these
results were consistent with the Popular Photography findings. The 50mm A
was sharper and much more contrasty wide open, and the Rikenon lagged at
the wider aperture settings. At f5.6 they were virtually identical in
performance, and by f8 there may be a slight, but ever so slight, advantage
to the Rikenon.
One interesting by product of this test was the observation of metering
differences between the Rikenon and the SMC-A. Basically, the Pentax lens
seemed to be a little less than a half stop faster, in terms of shutter
speed, at equivalent aperture settings. So, with both set to f8 the
Rikenon might meter at 1/90 while the SMC-A metered at 1/125. This
prompted me to compare all of my lenses that cover the 50mm range. To my
surprise, my three Ricoh 50mm's (1.2, 1.4, and 1.7) showed this speed
discrepancy on Pentax bodies. However, on a Ricoh body they metered
identically to the Pentax 50mm's. This suggests a slight (repeat: slight)
incompatibility between Ricoh lenses and Pentax bodies. It's hard to tell
how far off they are - certainly no more than a half stop. But, the net
result is that wide open, the SMC-A 50mm f1.4 and Rikenon 55mm f1.2 metered
identically in most situations -- undermining the advantage of the
'faster' Rikenon 55mm f1.2!
Here's a quick and dirty sampling of the results:
http://www.markcassino.com/lens_tests/slc_50mm.jpg
The scans show much more variance in exposure than the actual slides do,
but I wanted to avoid any 'tweaking' that could alter the results. But the
exposures produced by the scanner vary significantly. The samples are
small snippets from the middle left of the frame and show text, top to
bottom, at 5, 4, 3, 2, and then 10 point sizes. No unsharp mask or other
filters have been applied.
My conclusions: While I like the heft and the feel of the Rikenon 55 f1.2;
by this measure the A 50 f1.4 is a superior lens, especially considering
that used A lenses go for about $100 vs $150 for the Rikenons.
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Mark Cassino
Kalamazoo, MI
[EMAIL PROTECTED]
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Photos:
http://www.markcassino.com
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