film fogginggreenspun.com : LUSENET : Large format photography : One Thread
i have a problem that is driving me crazy. i have a problem with film fogging. i have tried different formats (4x5 and 8x10), as well as different batches of film. i process my film in btz tubes. the fogging is inconsistent. generally it is in the lower part of the negative, but not in a constant area. i have even switched areas of film loading. i don't think it is the camera, film, or holders. could it be the btz tubes and processing? i really have no idea what the problem is. about 50% of the time i get no fogging at all. also, i don't think it is the film loading since this is in an absolutely dark room (not even any fluorescent lights).
-- howard schwartz (email@example.com), January 02, 2002
Howard, Must be something in your processing equipment or procedure. Nonetheless check once more light tightness of your LF film holders and bellows, then try to process a film with TRAY SYSTEM in total dark: if no fogging will occurr, then your btz tubes aren't lightproof. I do suggest an accurate reading of AA book 2 (The Negative) If you don't have the book, buying it is worthy, no doubt! Do remember dark MUST be complete, when switch off your lamp, wait for a few minutes then check: if you have even the smallest vision of just a shadow, then here's the fogging reason.
Ciao Fabio Pollero Savona/Italy
-- fabio pollero (firstname.lastname@example.org), January 03, 2002.
If by the lower part of the negative you mean the area away from the code notches I would suspect you may be fogging the film when you replace the darkslide in the holder. If you insert it at an angle in direct light fogging can occur. I always do this slide replacement under my darkcloth.
-- jeff schraeder (email@example.com), January 03, 2002.
"If you insert it at an angle in direct light fogging can occur. I always do this slide replacement under my darkcloth."
Excellent point and I think you are correct. I also have a kind of dark cloth I put around the ground glass and film holder between removing the dark slide and making the exposure. Helps a lot, especially many older holders don't have much space between the end of the image area and the "ridge" stop.
-- David Stein (DFStein@mac.com), January 03, 2002.
It's a good idea to protect the camera back while inserting and removing dark slides. Also, I *always* clamp the holder/back unit closed with one hand while withdrawing or inserting the darkslide with the other. This also keeps you from levering the holder away from the camera as you move the slide--that's another excellent way to get fog. -------
-- Carl Weese (firstname.lastname@example.org), January 03, 2002.
Check your bellows. I think the chances are that you are experiencing this problem using a longer lens, where the bellows is 'exposing a small hole and leaking light'when extended, and when you are using a shorter lens the problem doesn't exist because the bellows is closed more.
I had the same problem a few years ago when using longer focal lenghts.
I can't see the problem lying with the holders because you say you have the same problem with both 4x5 and 8x10.. so how would that work??? You don't load the same film in the same holders do you?
Film holders when placed into the back of the camera are light tight, and even when the slide is removed they remain light tight, so forget all the nonsence that folks here are saying about drapping the dark cloth over the back of the camera to keep it dark.
You have a pin-hole in the bellows.
-- Nigel Turner (email@example.com), January 03, 2002.