>> >> I suspect that any
>> >> degradation caused by a high quality filter is minuscule. Poor
quality
>> >> filters are probably another story.
To which Kelton replied:
<< Hmm . . . I think this may call for another round of testing from Dr.
Reese. Gary, we'd like to see you redo *each* of your lens tests with
Olympus-brand filters . . . if it's (heh heh) not too much trouble . . .
>>
Right-O. Getting right on that!
Based on calculations I did, every single lp/mm (line pair per
millimeter) loss in resolution results in an approximate 0.1" reduction
in enlargability. My eyes can detect 5 lp/mm close up without glasses or
magnification. That equates to needing a A- grade lens to make a 5x7
print (assuming no loss of resolution in the printing process) that
would look critically sharp at the plane of best focus when viewed about
8" from my eye. For a 4x6" print, you can get by with a B grade lens and
still get critically sharp detail. An 8x10" print requires the likes of
the Nikkor 55mm f/2.8 resolution at 72 lp/mm. Of couse, the recommended
viewing distance increases as the print size increases. But how many
times have any of you critically examined a print as close as your eyes
can focus? If that is your test of print sharpness, than it behoves the
photographer to go to medium format or larger for print sizes of 8x10"
or larger, or limit oneself to slow films that are increasingly
disappearing from the market.
Along with the table I posted today, I did enough lens tests with
filters to give those interested a general impression of the
enlargability loss from using a filter. I say, "Why prove further what
has already become obvious?"
Gary Reese
Las Vegas, NV
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