I use an old Opemus III enlarger (6x6) for 35mm work (the condensers are not adjustable).
My main lenses are 50/2.8 (Nikkor and Computar), but the head does not rises enought to allow for cropping in 24x30 cm format.

So, I went after a 40/4 (in 'the' auction site) and, while the lens is quite decent and gave me the extra size I was looking for, there's an unusual problem when I mount it: an faint halo out of the image area.

Any clues on what is causing it or how to correct it?


Jorge O