another light fall-off question

[Nick Zentena]

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

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.

 

[removed account4]

talk to classic enlargers if you ever need omega parts!
he is very helpful, and a pleasure to work with!

while i have bought from glennview before, he is a bit expensive ...

good luck ...

john

 

[RJS]

If your lens is an f4 Nikkor it is their cheapie, four element model. These days enlarging lenses (used) are almost free. Good ones, that is. A 50mm f2.8 Nikkor on ebay shouldn't cost more than $25. If you're using the f4 Nikkor it is probably contributing to your problem. Slight falloff toward the edges is normal, but usually so little in most photographs that it isn't noticeable. A. Adams in his book on the print talks about dealing with this - but only on some prints did he feel the need.

 

[Lee L]

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

Painting with too broad a brush. The El-Nikkor 40mm f:4 N is 6 elements in 4 groups, and designed for higher magnification enlargements than the 50mm f:2.8.

Lee

 

[djkloss]

How does the Omega / Rodenstock 50mm f/3.5 fair? I also have one of these along with the Nikon EL 50mm f/4.