Dan Fromm
Joined: 14 May 2001
Posts: 2144
Location: New Jersey
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 Posted: Mon Sep 27, 2004 11:17 am Post subject: |
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On 2004-09-26 19:07, fifth quadrant wrote:
books in storage at moment. my phault! would someone please respond with a formula for calculating lens resolution. thank you.
a forum on "neat stuff" might be a thought or is that idea a thunk?
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Thunk? Thud is more like it. If you're the right age and grew up in Pittsburgh, PA, you're no doubt acquainted with Thud - The Magazine of Brick Throw.
To answer your question, a commonly-used rule of thumb calculates the diffration limit as 1500/f#.
So at f/2, diffraction limits the best possible resolution to 750 lpmm.
Understand that this assumes a perfect lens with no aberrations and no other problems, e.g., focusing errors, motion, that will reduce resolution. Remember too that this is aerial resolution, not resolution on film. In general, the best resolution attainable on film is limited by the film.
Bob Monaghan has posted a number of pieces on his site suggesting that the practical limit with real lenses, films, and photographers is not much over 50 lp/mm. Years ago Modern Photography did a study and found that under ideal conditions with the best lenses and emulsions available roughly 100 lp/mm could be obtained. Zeiss has claimed roughly twice as much, again under ideal conditions, to general derision. Ideal conditions are, in practice, unattainable.
What this all means is that you should quit worrying, try not to stop down beyond f/22, use a tripod, use a good grade of film, and be happy. Just go take pictures.
Cheers,
Dan |
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