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Re: [OM] A silly observation on Gary's lens test

Subject: Re: [OM] A silly observation on Gary's lens test
From: Gary Reese <pcacala@xxxxxxxxxxxxx>
Date: Thu, 23 Aug 2001 16:29:36 -0700
Another comment:

Popular Photography was giving at least B+ grades at f/16 in their SQF
testing . See their results, which I posted along side mine for the
35-70mm f/3.5~4.5 and 35-80mm f/2.8 Zuikos.

Theoretically the image should deteriorate after the optimum aperture.
But, we just don't detect it till it reaches a threshold deterioration.
For pure resolution, that threshold is taken to be 5 l/mm.

I was also factoring in contrast to my SQF grading.  That typically
deteriorated at f/16 or f/22, with f/32 and wide open results often
quite a bit lower.  The best lenses showed little difference across
their aperture range.

To choose a methodology that shows detectable deterioration after
optimum aperture requires a remarkable film and probably a larger
reproduction size.  It wouldn't do me any good to evaluate the old
slides at 100X, since the film was the limiting factor.

Gary Reese
Las Vegas, NV


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