Lens problem?greenspun.com : LUSENET : Large format photography : One Thread
A friend of mine bought a used Fuji SWD 5,6 / 90mm lens ( serial n° 570...) and mounted it on either a Sinar F1 or an Arca Discovery. The images made with the two cameras at f:22 and infinity are sharp on the 4/5 part of the film but are unsharp along a linear vertical strip at the left side. This problem can be seen on the ground glass of both cameras, so I do not think it comes from the camera itself nor from the fidelity holders ( the Arca is new and so the Fidelity's). Could this problem come from the lens? There is no washer between the two parts of the lens but the front part of the lens is mounted on the lensboard with two thin washers in between. Is it a proper way of mounting this lens? Can someone explain?
-- A. Mouton (firstname.lastname@example.org), November 15, 2001
Have you tried rotating the lens to see if the problem rotates with it?
-- Chuck Pere (email@example.com), November 16, 2001.
I was going to suggest that it is the film holder, but since you see it on the ground glass, that rules that out.
That seems to be kind of a weird problem for a lens.
I'm not familiar with the Fujis. Do they have a little anti-rotation mounting screw on the mounting surface of the front element like my Schneider has? This screw is meant to go through a small hole in the lens board to keep the lens from rotating. Many people just take it out. If you have a screw like that sandwiched between the front element and lens board, your lens axis might not be normal to the film plane.
Go in a dark room, but a light bulb in the back, and see if any light is leaking around the lens/lens board interface.
Are you able to adjust focus and get a sharp image along the normally fuzzy part?
I think using two different camera would rule this out, too, but are you sure that everything is zeroed correctly? Sounds like you might have a tiny bit of lens swing.
-- John H. Henderson (firstname.lastname@example.org), November 19, 2001.