another light fall-off question

youngrichard said:

djkloss said:

I have just run into this problem which I had not had before, printing 20x16 from a 35mm neg on a Durst DA900 with Ilford 500 head. I have limited headroom in the cellar so to get 20x16 I swapped from my usual El-Nikkor 50mm f2.8 to an Apo-Componon f4/45mm lens and printed with lens wide open. Light fall-off at edges was like a vignette. Looked in all my technical books - nothing on the subject. Investigation with meter showed fall-off at edge was 1 1/2 stops at f4, but this reduced to 1/3 stop at f8, which when printed is barely discernible, or at least OK so far as I am concerned.
I've got "Basic Photography" and "Advanced Photography" by M J Langford; Ansel Adams "The Print"; Tim Rudman's "Master Printing Course"; and manuals for various enlargers. Advice to stop down a couple of stops is frequent but relates to edge sharpness; no one seems to mention reducing edge light fall-off. Or have I missed it? It seems important to me; but perhaps it is just a problem when using a wider angle lens than recommended to avoid swivelling the head and printing on the floor.
Richard

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It's a coverage issue. At smaller print sizes you're gaining coverage the same way a LF lens would with a closeup. With larger prints you're pushing the lens close to infinity. Stopping down I guess gains you some coverage.

I bet you don't see this issue with smaller prints right? Set up the same lens for an 8x10 or 5x7 size print and measure the falloff.

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RJS said:

If your lens is an f4 Nikkor it is their cheapie, four element model.

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