Help identifying light leak or processing error

I decided to try out my new Chamonix 4x5 camera and get some practice with it today. After developing the negatives I noticed some issues. I've attached images of my negatives with the problem areas marked in red. I'm guessing there has been some sort of light leak since parts of my images are darker than the rest and the film registers look fogged.

-Each page of negatives was processed separately in a Stearman Press SP-445 film processing tank. I have used this tank a few times before without issue.
-Film was loaded completely in the dark into brand new Toyo film holders.
-I have checked the camera for light leaks with a flashlight in the dark.

I don't think there was a light leak when loading the film holder in and out of the camera and I have a hard time imagining that I could have fogged the paper in this way when loading and unloading the film. I suspect the film developing tank might be the issue, but then again it worked fine up until this point and I don't think that would cause some of these straight lines. Additionally, the same issue has manifested in two separate batches.

Anyone have any ideas?

Several years ago there was a problem with Toyo's darkslides. Check yours in total darkness with a very bright light.

Because the dark area's are on the film rebate as well, i think the film must have been exposed to a bit of light either while loading the film into the film cassettes or while loading the film into the developing tank. Another option is that the filmboxes you have used ain't completely light tight. Where and how did you load your film?

The light leaks I've had were more obvious, but because you have two or three that look exactly alike and are low intensity, I'd suggest running several tests -- and unfortunately use some film.

First, your film holders -- unless you are sure they are OK. Just put film in the holders (at least one for a start) and expose them to sunlight.

Next, camera. Put film in a known good holder, remove dark slide carefully and leave it in the sunlight -- lens closed, bellows extended.

Simply over-develop the film to help leaks show up. Any leaks?

Check your film holders possible with photographic paper in the sun, even though you do not think it is them. If that is not it, check you film boxes.

That's a GREAT idea. That will work BETTER than using film, and will be a LOT CHEAPER.

Hi everyone, thanks for the replies! I think testing the film holders using paper is a great a idea. I'll try to do that as soon as I get some time. I also have some CatLABS X Film 80 I can use to test if I need something more sensitive than paper. This batch of film is kinda junk, it has some emulsion defects that make it a bad choice to use for anything serious.

Anyway, I wanted to post an update. I had two more holders of film to develop. These particular holders, while older, I know are good. I also loaded the film into these holders at a different point in time than the film that was fogged. This film was shot using the same Chamonix camera. The film came out with no issues!

While I cannot rule out my film holders yet for all the issues yet, based on the stripped border on the one fogged negative and the fogged film register, I suspect a light leak with the Stearman Press tank. The internal light baffle and edges of the tank film holder kinda line up with those stripes and could be from a shadow. I also found this linked forum post that looks like a similar issue and may back this up.

https://www.largeformatphotography....hp?157509-Light-leak-driving-me-mad-for-weeks

With the SP445, you need to make sure the baffles are installed in the correct order. Mine's set up so that looking down, from outside edge to inner, it's "- - -" followed by " - - ", followed by the heavy rail that supports the holders.

It's also a good idea to take the o-ring off on occasion, roll it around a bit, and put it back on in a different position, and of course, it should be in the groove all the way around.

Finally, when I close the tank, I pull down with my fingers in the middle of the top-- makes it much easier to get the top snugged all the way down.

grat said:

With the SP445, you need to make sure the baffles are installed in the correct order. Mine's set up so that looking down, from outside edge to inner, it's "- - -" followed by " - - ", followed by the heavy rail that supports the holders.

It's also a good idea to take the o-ring off on occasion, roll it around a bit, and put it back on in a different position, and of course, it should be in the groove all the way around.

Finally, when I close the tank, I pull down with my fingers in the middle of the top-- makes it much easier to get the top snugged all the way down.

Click to expand...

I did check that the light baffles are in the correct order. Would you recommend greasing the O-ring? The forum post I linked in my previous comment mentioned that.

I haven't, but mine does leak on occasion. I assume whatever daylight tank I'm using will drip to some extent or another, and put down one or two of the light blue scot paper shop towels.

the squeeze-and-thighten routine on the SP-445 generally prevents leaks for me, unless I overfill, and there isn't enough room to squeeze much air out. I've never greased the o-ring, but I do periodically grease the caps becuase I hate that they are really hard to remove and have no lugs for me to grip.