Please help me figure out this light leak. I'm loosing my mind!

cirwin2010 · Sep 15, 2022

I made a similar thread a few months back, but I'm making a new one since I have done some testing.

Problem: Most of my hp5 4x5 negatives are fogged. The side of the film with the notch codes will be darker than the other side and it forms a bit of a gradient. The fog is present in the film rebate area which is where it is most obvious. I will occasionally get a "clean" negative, but I cannot pinpoint the cause of the problem. I originally thought it was an issue with my sp-445 developing tank, but switching to a Paterson tank has not resolved the problem. See first attached image.

Equipment:
-New Chamonix 45F-2 camera
-New Toyo film holders and older Riteway & Lisco Regal holders

What I have tried to reproduce the issue (see second image):
1. Developed a negative from my box of new film to see if the box got fogged. Negative came out completely clear
2. Put a film holder into the camera, removed the dark slide, and shined a bright light on the camera to check for light leaks. Negative came out completely clear.
3. Put a film holder into the camera, removed the dark slide, and pulled the film holder slightly away from the body. This was an attempt to compare this type of light leak to what I have been getting. Negative rebates came out completely clear unlike the "bad" images.
4. Over exposed an image in camera to test if the issue is light piping or internal reflections from long exposures. Negative rebates came out completely clear.
NOTE: all above tests took place with Toyo film holders since these are what I normally use.

The above tests would lead me to believe that "bad negatives" I have been getting were a fluke. However, I went and shot more hp5 after and got more of the same results. I also exposed some fp4 in some Riteway film holders. The film rebates on those are completely clear. I am uncertain if the problem with my other negatives simply did not occur for those images or if the film is not sensitive enough to show the problem.

This problem is really dragging me down. I want to use my new 4x5 camera for my serious projects, but I cannot with these unreliable results. Please help me.

John Salim · Sep 15, 2022

I'm wondering if the sheets have somehow been fogged in the film box itself.
Do you use the three part box as properly intended along with the inner lightproof bag ?

John S

glbeas · Sep 15, 2022

Yes a bit of history of the box of film would be appropriate. If you bought the box open mishandling is suspected.

cirwin2010 · Sep 15, 2022

glbeas said:
Yes a bit of history of the box of film would be appropriate. If you bought the box open mishandling is suspected.

John Salim said:
I'm wondering if the sheets have somehow been fogged in the film box itself.
Do you use the three part box as properly intended along with the inner lightproof bag ?

John S

I would have thought the same thing. But my testing would have ruled out fogged film in the box. This issue has also survived two whole boxes of HP5 and now starting on a third. My test of developing a sheet straight from the already opened box came out clear, along with some of those other tests. I am using the three part box + bag.

Doremus Scudder · Sep 15, 2022

Some Toyo holders had trouble with the dark slides not being completely opaque. See my reply to your question over on the LF forum.

Doremus

Sirius Glass · Sep 15, 2022

If the film is fresh then the problem will be coming from light leaking in around the dark slide or not blocked from entering when the dark slide has been removed. That would explain the variation in the fogging. Buy some new film holders and see if the problem goes away.

Europan · Sep 15, 2022

How do you bring film and developer together? I see overly dense film edges with all samples. How do you develop?

Donald Qualls · Sep 15, 2022

Fogging in the rebates when testing shows clear rebates suggest there's something happening with film that stays in the film holder longer. Chemical fogging and radiation could do this (though almost all radiation sources in a typical home are primary alpha emitters, and alpha is ridiculously easy to shield against). Try putting a fresh sheet in a film holder, and leaving it on the darkroom counter for a while, with another sheet kept in your camera bag for a few days? Keep track of which is which, of course.

cirwin2010 · Sep 15, 2022

Europan said:
How do you bring film and developer together? I see overly dense film edges with all samples. How do you develop?

Even the completely clear sample you think is dense? Looking at it under a loup I hardly seen any grain and it seems about the same as my 120 negatives.
I develop my HP5 in HC-110 dilution B for 5 minutes at 68F. Depending on the tank, I perform 4-5 every minute for 10-15 seconds.

jnk · Sep 15, 2022

write to toyo and ask for new dark slides

Donald Qualls · Sep 15, 2022

Paterson tanks have no soft light seal parts -- at least not the Super System IV family. The lid latches into place without anything resembling a gasket. The inversion cap does seal, but it's irrelevant to light tightness.

Not to mention this has persisted over two completely different system tanks.

grat · Sep 15, 2022

The fact that it extends into the rebate area suggests it's either happening outside the camera, or there's a leak in the film holder itself.

I'd test the darkslide (unlikely, but possible) for transparency, and try flipping the holder open and shine a light through the flexible "hinge" of the film holder.

.... do you own any thoriated lenses?

jnk · Sep 15, 2022

how do you load your film holders, in a dark bag and film in tank? in a room ? do you have glow in the dark buttons on your enlarger switches or load your film and develop it near a gray lab timer that glows in the dark?
if it is a dark bag sometimes light leaks in through the sleeves and zipperedbaffle, if in a dark room, it might not be completely dark. light likes to leak into places that seem dark glow in the dark things, put something on top of them and turn it upside down if it is a enlarger switch if it is your gray lab timer cover it and point it away from you.

Europan · Sep 16, 2022

cirwin2010 said:
Depending on the tank, I perform 4-5 every minute for 10-15 seconds.

Invitation for irregularity. The baths should be never be standing. Use a softer formula and keep constant agitation in a larger tank. The unexposed areas ought to turn out blank as can be. I develop 4" × 5" sheet film in deep ice-cream containers. Detlef Ludwig, the founder of Gigabitfilm, gave me that hint.

Donald Qualls · Sep 16, 2022

Europan said:
The baths should be never be standing. Use a softer formula and keep constant agitation in a larger tank.

This is another religious argument like stop bath or not. I've gotten good results with intermittent agitation (i.e. same as a roll film tank) since I started shooting sheet film in 2003. Even in the frequently reviled Yankee Agitank (once I figure out how to agitate it).

grat said:
.... do you own any thoriated lenses?

But those wouldn't fog under the film guides; those are usually metal and would provide excellent shielding from the alpha and beta emissions of a thoriated lens element (and any gamma from these is so weak as not to matter unless you leave the lens sitting right on the film with the dark slide out).

cirwin2010 · Sep 16, 2022

Europan said:
Invitation for irregularity. The baths should be never be standing. Use a softer formula and keep constant agitation in a larger tank. The unexposed areas ought to turn out blank as can be. I develop 4" × 5" sheet film in deep ice-cream containers. Detlef Ludwig, the founder of Gigabitfilm, gave me that hint.

Like the other commenter said, this is all down to personal preference. Some people prefer constant agitation and other prefer intermittent agitation. Both I think can be valid dependent on routine. The theory of intermittent agitation with compensating developers is that it allows the developer solution in the highlights to exhaust somewhat while the shadow areas continue development. This helps control contrast. How often you agitation will further effect contrast.

I have a routine I adopted from another source for my Across II shots. I frequently shoot in low light situations with bright points of lights and I've had extremely good success with the following.

Across II shot at ISO 100
Rodinal 1+100 @ 68F
Agitation: 18 minutes total, 15 seconds per minute for the first 3 minutes followed by 1 inversion every 3 minutes.

cirwin2010 · Sep 16, 2022

grat said:
The fact that it extends into the rebate area suggests it's either happening outside the camera, or there's a leak in the film holder itself.

I'd test the darkslide (unlikely, but possible) for transparency, and try flipping the holder open and shine a light through the flexible "hinge" of the film holder.

.... do you own any thoriated lenses?

I'm going to test my film holders later. I have some catlabs 80 film that I don't really like that I will try to use for my test. Only thing is that this is a slow film and I worry I may not see any results. But I will try that first before using my more expensive HP5.

And I don't have any radioactive lenses.

Donald Qualls · Sep 16, 2022

Something else that occurred to me -- I recently bought a refurbished watch with luminous hands. NOT the kind with radium; this one is technically phosphorescent; exposure to light stores energy in the luminous paint which is then released slowly at a particular shade of yellow-green over many hours. When fresh out of the sun, the hands are bright enough to see the glow in indoor room light; near dawn after 6-7 hours of sleep I can barely make them out in a dark room.

The connection here is that if you have such a luminous watch, it will be brighter soon after spending time outdoors (in daylight) than it would be after working in the darkroom -- which could lead to more fogging with "real" negatives than in tests. Just as I leave my smart phone outside the darkroom when I'm handling film, I'll be leaving my watch beside it when I need total darkness -- because my wrist is just a couple inches from the film when I'm loading or unloading film holders and putting the film into a developing tank. This precaution is also applicable to smart watches, which can light up inside a changing bag without you even being aware it has happened -- until you see the fogged film.

cirwin2010 · Sep 16, 2022

jnk said:
how do you load your film holders, in a dark bag and film in tank? in a room ? do you have glow in the dark buttons on your enlarger switches or load your film and develop it near a gray lab timer that glows in the dark?
if it is a dark bag sometimes light leaks in through the sleeves and zipperedbaffle, if in a dark room, it might not be completely dark. light likes to leak into places that seem dark glow in the dark things, put something on top of them and turn it upside down if it is a enlarger switch if it is your gray lab timer cover it and point it away from you.

Donald Qualls said:
Something else that occurred to me -- I recently bought a refurbished watch with luminous hands. NOT the kind with radium; this one is technically phosphorescent; exposure to light stores energy in the luminous paint which is then released slowly at a particular shade of yellow-green over many hours. When fresh out of the sun, the hands are bright enough to see the glow in indoor room light; near dawn after 6-7 hours of sleep I can barely make them out in a dark room.

The connection here is that if you have such a luminous watch, it will be brighter soon after spending time outdoors (in daylight) than it would be after working in the darkroom -- which could lead to more fogging with "real" negatives than in tests. Just as I leave my smart phone outside the darkroom when I'm handling film, I'll be leaving my watch beside it when I need total darkness -- because my wrist is just a couple inches from the film when I'm loading or unloading film holders and putting the film into a developing tank. This precaution is also applicable to smart watches, which can light up inside a changing bag without you even being aware it has happened -- until you see the fogged film.

I always remove my watch before doing any sort of darkroom related work so I don't risk fogging anything. It also would catch on the film changing bag if I didn't.

Donald Qualls · Sep 16, 2022

cirwin2010 said:
I always remove my watch before doing any sort of darkroom related work so I don't risk fogging anything.

Good practice. It was worth mentioning, in any case.

glbeas · Sep 16, 2022

If you have a good bright flashlight pull a darkslide out and cover the end of the lit flashlight with it in a dark room. You shouldnt see any glow through the plastic.

Bill Burk · Sep 16, 2022

Doremus Scudder said:
Some Toyo holders had trouble with the dark slides not being completely opaque. See my reply to your question over on the LF forum.

Doremus

Ah but the rebates would be clear if darkslide wasn’t opaque

Bill Burk · Sep 16, 2022

My best guess is that the fog comes in handling. You may not have a completely dark darkroom or a glowing LED bulb when you take the film from the box and load in the holder, or out of the holder into the tank.

Bill Burk · Sep 16, 2022

Ah you mentioned a changing bag. Make sure the elastic is snug and that you are in a pretty dim location to begin with

Sirius Glass · Sep 16, 2022

cirwin2010 said:
I always remove my watch before doing any sort of darkroom related work so I don't risk fogging anything. It also would catch on the film changing bag if I didn't.

I too remove my watch which does not have any glowing parts but I do not want to have it catch on the sleeves of the changing bag or anything else.

Please help me figure out this light leak. I'm loosing my mind!

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