I've been doing some number crunching to find an optimal aperture for a shoot. It's full length portraits with a Gowlandflex 4x5 and 180mm f/5.6 Symmar S, and the print sizes will be up to 40x50", prints viewed at 1m distance. I need roughly three meter shooting distance and 50-100 cm DOF to fit the model comfortably in the frame, and keeping her sharp from shoulder to shoulder even with profiles.
Plugging in the data to Cambridge In Color's DOF calculator yields required aperture of at least f/22, depending on the eyesight setting. Diffraction calculator claims that I would be diffraction limited starting at f/32.
Given the fuzziness in all of the above, my conclusion is that f/22 is a fitting compromise for full length portraits for medium/large prints with a 4x5. I've shot before with f/16 and have been happy with the results, but the prints have been significantly smaller.
Any comments or disagreement from you who have more experience with large formats?
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