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

[cirwin2010]

Okay everyone, I did some more testing and it has just left me with more questions than answers. Without going into all the details I think I can rule out bad film holders as the issue. I also think I can rule out light leaks in the camera causing the issue as well.

My last shoot consisted of HP5 loaded into two different types of film holders (Toyo & Riteway), and while the film edges don't appear fogged at first glance, compared to other negatives I have shot, they are slightly darker. With further inspection, the edges with the notch code are slightly darker on most of the shots (doesn't matter which film holder used). All the film in this "session" was loaded at the same time and developed in the same tank. Why are the rebates of some of the negatives darker than others? Shouldn't they all be the same?

I ended up taking a deep dive into all the 4x5 film I have ever shot. I have walked away with the following conclusions:
1. The problem only exists in my HP5 negatives, but the sample size of Catlabs 80 and FP4 film is comparatively small.
2. About 50% of my HP5 4x5 negatives display fogging and/or elevated base+fog
3. The edge containing the notch code is usually more fogged than other edges
4. The issue has occurred through 3 separate boxes of HP5
5. The issue has occurred through a variety of film holders and is intermittent with the same film holders

Concerning my development routine:
1. I use HC-110 dilution B or film rated iso 400 or higher
2. I only use HC-110 as a "one shot" solution
3. I use Ilford Rapid Fixer 1+4
4. Fixer is periodically replaced
5. Fogging issue is not linked to any changes in my development routine
6. Fogging does not occur with 120 roll film using the same development routine

Concerning my darkroom and film loading routine:
1. Film gets loaded into my developing tanks using a dark bag
2. My dark bag is known to be good. I have developed countless rolls of 120 film using this bag
3. For 4x5 I use a Paterson style tank and SP-445 and both have exhibited the fogging issue. I used a smaller Paterson tank for 120 film and that has never had a problem with light leaks
4. I load my 4x5 film into film holders outside of my changing bag to reduce dust issues and aid in ease of loading
4a. I perform this in my blacked out basement
4b. Only done at night with lights on the flood above turned off as my basement is not perfectly light sealed during the day
4c. All light sources are either turned off or covered
4d. I scan the room each time to check for any light sources after my eyes adjust


After reviewing all of my previously developed film and trying to replicate the issue, I'm looking at my film loading routine. Specially loading my film into the film holders as this occurs outside the dark bag.

Is it possible that there is some source of light that is not visible to the naked eye fogging a faster film (like HP5)? With paper you can get away with your darkroom not being perfectly light sealed, but film is obviously a lot more sensitive and iso 400 film is more sensitive still.

Is there any chance that long exposures (measured in minutes) could result in light piping through unexposed areas? I doubt this as not all my negatives shot in this way display this issue. But, of my last batch of developed film there was one negative that was more "fogged" than the others and this one happened to be overexposed in camera. Could be a fluke though.

There are two tests that seem obvious to me at this time:
1. Replicate my darkroom conditions for loading film and leave a sheet out for a long time then develop it. Check for any fogging.
2. Use my dark bag to load my film holders. I don't really want to do this because of dust, but I may need to for informational purposes.

[Vaughn]

If you can't see the light, there is none...especially after several minutes in the dark. Keep your eyes open.

One main clue is more fogging on the notch end. When is that end of the film more suspecptable to fogging than the other end?

[cirwin2010]

If you can't see the light, there is none...especially after several minutes in the dark. Keep your eyes open.

One main clue is more fogging on the notch end. When is that end of the film more suspecptable to fogging than the other end?

When I take the fresh film out of the box, I keep in in that cardboard folder its in. The notch side of the film and the adjacent boarders would be a bit more exposed I suppose. When loading the film holders, the notch side of the film would be exposed for very slightly longer than the rest. That is the only thing I can think of.

Also when I load film into my developing tanks, the notch side of the film is always facing up. But I put more than enough chemistry in my tanks to ensure that the film is covered.

[sharktooth]

Did you buy all your boxes of HP5 from the same store? Maybe they've got some issue with how they store the film (near a heat source maybe). it's still grasping at straws though.

[Vaughn]

When I take the fresh film out of the box, I keep in in that cardboard folder its in. The notch side of the film and the adjacent boarders would be a bit more exposed I suppose. When loading the film holders, the notch side of the film would be exposed for very slightly longer than the rest. That is the only thing I can think of.

Also when I load film into my developing tanks, the notch side of the film is always facing up. But I put more than enough chemistry in my tanks to ensure that the film is covered.

In those situations, the non-notch areas are more protected. Those are the times that need more attention. What is the possibility of an intermittent light in your film loading area? The fogging is being done from the notch end downward, slowly lessening. Light from one end would cause an even gradation like we are seeing.

IMO, it is not heat or chemical damage (that would be all or nothing), and not happening when the film is in the holders -- looking at the negatives rule that out for me. I spent a couple decades trouble-shooting students' 4x5 problems. Most likely not a factory-related problem...just one isolated case (single user) like this would be strange.

Keep on truckin'!

[sharktooth]

Some humidifiers and dehumidifiers use UV light to kill bacteria. You'd think devices like that would be well shielded, but who knows.

[Chuck Pere]

To get a more accurate check on film fogging you might want to give an unexposed piece of film a small pre-exposure. The film might be slightly fogged but not up to the threshold that is needed to show a density when developing an unexposed piece. If interested, you can search for film pre-exposure to find out how to do it.

[Doremus Scudder]

cirwin2010,

From your detailed explanation, I would, as you do, think to examine your film loading area for extraneous light sources. Don't just look from a standing position over the loading surface, get down to counter level and look from there. A mirror laid on the loading surface will help you to see what the film does as well. It doesn't take much of a leak to fog film that much. Phone screens, smart watches, indicator lights on things like electronics or GFI outlets, light from cracks in walls and window/door frames, etc., etc., are all enough.

A test might be to load a few holders in the dark bag (as much as you hate to do it) and see if any of those end up with the same fogging after exposing and developing.

There is a reason for this, so keep looking.

Best,

Doremus

[grat]

I'm starting to think UV or IR light coming from some source. FP4+ doesn't extend quite as far into the UV as HP5+, and it's slower speed.

If you've got a digital camera, try taking a really, really long exposure of your darkroom and see if anything lights up.

Or, if you have a friend who's into photography and hates you, see if someone put a glow-in-the-dark sticker inside your dark bag.

[cirwin2010]

I think I found the issue! TL;DR I think its stray light when loading the film holders.

I went out to shoot yesterday morning with film holders loaded up with HP5+ and FP4+. For each scene I took a shot on both film stocks. When developed the HP5+ displayed the same fogging as all my previous shots, but the FP4+ was not effected. Both were loaded at the same time in the same conditions.

Still trying to find evidence of the problem, I developed out four sheets of unexposed HP5 that I had loaded at the same time. Again, these were not loaded into the camera at all nor had their dark slide removed under any condition other than loading or unloading the film. This time, I got results.

The attached images are of the same negatives, but I tweaked the contrast of the second to try to better show the issue.





The fogging is not as obvious as on my other negatives, but it is there. If you look closely you will see a few things:

-There is slight fogging extending inward from the top and bottoms of the negatives
-One negative shows a clear line where light was blocked by the dark slide before I closed it all the way. Film rebates are also visible from light blocked by holder edges. A slight line if visible in person on another negative.
-There are a couple light patches near the edges of the film. I believe these are where light was blocked by my fingers when handling the film. This is more visible in person.

I think these negatives are clear evidence that the source of the fog is from something in the environment when loading the film. I still am unable to detect any light in my basement, but clearly there is a source of something that is not visible to my eyes that the HP5 is sensitive enough to pick up. I can't think of any sources of UV or IR in my basement, and I don't think there is anything radioactive down there (I hope).

I think my next course of action would be to get a fresh pack of HP5 and start using my dark bag for loading again. Not thrilled about that since it is a bit cumbersome and its harder to keep dust free. A changing tent may be a good investment, though expensive. Also maybe geiger counter as something to toy with