Please help me identify the source of this light leak on my negatives.

[Doremus Scudder]

Maybe someone opened the box of film when the lights were on? Try developing a sheet directly from the box to see. Check the box for damage/holes as well.

Doremus

[Deyoung]

Would radiation be able to cause something like this? An old CRT screen (TV or Computer Monitor), microwave? or a high level of radon? It would seen these may have an effect, but only seen on higher asa film stocks. Just wondering out loud.

[cirwin2010]

Would radiation be able to cause something like this? An old CRT screen (TV or Computer Monitor), microwave? or a high level of radon? It would seen these may have an effect, but only seen on higher asa film stocks. Just wondering out loud.

Probably not. I'm not sure if radon gas would cause film to fog, but I got my basement tested for that and it would have effected roll film in my changing bag if it even could be a cause. I would also think that if putting slow film through an airport x-ray machine is "safe," then anything at home that is strong enough to fog film is likely a great cause for concern.

[Bill Poole]

+1 for developing a sheet directly from the box. Then from that box, or better yet a new one, maybe take a single sheet and leave it naked to your darkened loading area for perhaps 10 times longer than it would be exposed during loading. Develop both. If the first sheet is unfogged and the second one is distinctly fogged-- that would confirm your suspicion, yes? But I am betting that if you can't see light in your loading area after a few minutes with the lights out, then that is probably not the problem. Sorry for hassle. Must be very frustrating.

[Tim V]

I've been having a similar issue recently. At first I thought it was the tape seals / hinges of my 8x10" holders, but the more I thought about it and the longer I waited in the darkroom for my eyes adjust, I found the issue. Light was leaking in through a light fitting via the ceiling cavity. Impossible to see with the naked eye unless I'd been in the dark for more than 5-10 mins, but plain as day after that. It was so subtle I think under most circumstances it'd not cause a problem, but when loading film into my Jobo expert tanks I leave the the ends of the film sticking slightly above the tubes so I know which cavity has been loaded. Long story short, the first sheet loaded exhibited the worst effects, down to the last which was negligible. I'm really annoyed at myself, but live and learn. I can print them acceptably with extra care, so that's something.

[Vaughn]

Sheets have been developed straight from the box. (no fogging)
Film was NOT fogged while it was in the holders/camera. (rebate fogged)
NOT chemically fogged. (pattern of fogging).

I'll stick with poor handling while loading/unloading film from the holders.

[cirwin2010]

So I was wrong about everything. It was the Paterson dark bag. Turns out it actually isn't that dark. Was pretty apparent when I stuck my head in it near the light where I work. This would explain everything every single issue I've had. Never was a problem with my roll film due to how I would load that and it being a quicker process. The intermittent issues were from whether or not I had a particular light on in my basement when using the dark bag.

Sadly I think I may have lost over $100 of film though. Confident that the issue was from my space when loading outside of the dark bag, I loaded a bunch of Fp4 and HP5 last night from fresh boxes of film in my dark bag. This was in anticipation for a trip I'm taking today. But as a sanity check this morning I developed out a holder of hp5. I expected it to come out blank, but it was very fogged with shadow marks from the dark slide being partially removed. All of my film is potentially fogged now....

So turns out my dark space was fine, but the dark bag very much wasn't. I would have expected better from the Paterson bag, but it looks like I may need to look at a more expensive option.

Any suggestions on an actually "dark" bag/tent?

[jnantz]

if your space is dark and not light-leaky do you need a dark bag too ?
I would spend time making sure your space is light tight so you can load your film developing tanks and film holders
without the need of a dark bag. those things are always suspect

[cirwin2010]

if your space is dark and not light-leaky do you need a dark bag too ?
I would spend time making sure your space is light tight so you can load your film developing tanks and film holders
without the need of a dark bag. those things are always suspect

My basement is the only place in my house I can black out. But i isn't light leak free until night with all lights on the floor above turned off. It's definitely not dark enough for film during the day. It's not convenient at all hence why I use the dark bag for unloading the film typically. I think I may just need to buy a nice dark tent for loading film, it's just too bad they are so expensive (at least on B&H). But, might be worth it considering how much film I've burned through trying to figure out the issue.

[Bernice Loui]

See post# 19..
https://www.largeformatphotography.i...egatives/page2

Highly suggest giving up the idea or try using a dark bag or "film" changing tent. IMO, they are a great source of great grief over the passage of sheet film usage. They all fail eventually, not a matter of if, matter of when.. and they usually fail with zero warning causing !_!_!_! when failure from light leaks can be least tolerated.

The better way, simply load as many film holders as needed and a few extra if needed in proven dark and film exposure safe area. This same area also serves to unload film and loading the exposed sheet film for processing.

You've lost FAR more than $100 over this episode.. consider your time lost (not replaceable), frustration, resources spent and much more.... what happened is waing to happen again if the dark bag/film changing tent is used again.

Personally, taken anywhere from 4 to 30 loaded film holders (5x7 or 13x18cm) on trips that go for a day or more days in the camera outfit case or a seperate film holder case. Make absolute sure ALL film holders are good with ZERO light leaks before doing this.


Bernice

My basement is the only place in my house I can black out. But i isn't light leak free until night with all lights on the floor above turned off. It's definitely not dark enough for film during the day. It's not convenient at all hence why I use the dark bag for unloading the film typically. I think I may just need to buy a nice dark tent for loading film, it's just too bad they are so expensive (at least on B&H). But, might be worth it considering how much film I've burned through trying to figure out the issue.