Film Fogging

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,

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.

 

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Ciao

Fabio Pollero

Savona/Italy

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.

"If you insert it at an angle in direct light fogging can occur. I

always do this slide replacement under my darkcloth."

 

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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.

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.

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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.

 

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I had the same problem a few years ago when using longer focal

lenghts.

 

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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?

 

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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.

 

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You have a pin-hole in the bellows.