Light leaks

Compiled by Q.-Tuan Luong for the Large Format Page

Some photographers (like me) are plagued by these problems, which are among the worse frustrations of LF. Some have never experienced them. There are zillions of different sources of light leaks.

A summary

Richard Knoppow

A few diagnosis remarks

If the fogging extends past the borders from the rails in the holder it has to be coming from elsewhere than from the camera. If many negatives have identical an identical or nearly identical fog pattern it may come from a leak in the film box. Richard Knoppow

Pinhole leaks would be more likely to look like superimposed images than oblong blobs. Paul Butzi

If the "light leaks" do not have sharp edges but they do have edges, i. e. there is not a bright area which gradually fades out, this must be not too far from the film. If the leak were in the bellows or in the front board then I would expect the bright areas to have foggy edges. Eberhard Funke

Leaking film holders

Common problems

Check the condition of the hinges on the loading flap. If they are worn that could be your leak. Is the slide seating all the way down into the holder? Maybe you have a small hairline crack at the seam of the flap possibly?

One place they leak is the place where you pull out the dark slide. Ever take a holder apart? A friend and I did when we where building a vacumn 4x5 film holder for our astrogrpah (that's another story). Inside the "top" of the holder, behind the metal part, is a peice of light brass - it looks like a curved comb. over top of this metal is a peice of black felt. What happens over tiem is the felt wears down, "teeth" on the comb loose thier spring and fail to hold up the felt in place, or break all together. Normally when you pull back a darkslide, the curved part of the "comb" springs back up into place, blocking off light. Older holders, the felt may have holes in it, allowing small light leaks to escape through. Also, the felt may be very dirty, so no matter how clean the rest of the holder is, you continually get scratches and dust marks on your flim, carried in off the felt onto the emulsion of your film from the darkslide being pushed in. Joseph O'Neil

You can check these with a flash light by folding down the loading flap so you can look straight into the holder and shining the light right into the slot for the slide. Richard Knoppow

Marking holders for identification

If large format users would use a notch-encoding scheme to number their holders, it would be MUCH easier to exactly pinpoint a leaky holder. I (and several other large format people I'm friends with) take miniature files and notch the flap with the files. For me I use a v-notch for 1-4, square-notch for 5, and a half-round- notch for 10. Thus, the holder that I've designated to hold sheets 9 and 10 has a square-notch and 4 v-notches on the 9-side, and a half-round-notch on the 10 side. Should either side of that holder ever leak, it'll be really obvious as to which holder (and side) is the culprit. NOTE: the notch goes into the side that contacts the film, since light hits the ends of the holder at an angle, there is no need to notch both sides of the flap. Be sure to clean off the residue with an X-acto knife and clean the plastic dust out of the holder when you're done. Dean Barto

To identify leaking holders among a large set

The best that we came up with was to load them with the cheapest paper that you can get (pre cut to 4x5 will save time) and take them out into the sun and twist each one so that all surfaces face the sun (remember paper is a lot slower than film therefore keep them in the sunlight about 5 times longer than usual) Advnatage: you can load them under a safelight. If you are really cheap and can spend the time, you can use the same sheet of paper for more than one holder to narrow in on faulty ones. [Algorithm to determine the minimum number of light sensitive sheets to identify all leaky holders left as an exercise for the reader] Don't forget to number all holders (and matching sheets of paper before you start). Sandor

Leaking camera

How to find a leak

I would take the camera into a darkened room and remove the lens board. I would shine a light into the camera body to see if there is a light leak in the bellows or the back. If no light can be seen, put the lens board back on and take the back off and shine the light in from that end and inspect for leaks in that direction. More than likely, you will find the leak and patch it with black tape and be back on the road in no time. Lee Carmichael

Just to suggest another, more definitive, way of finding those pesky pinhole leaks: if you are in a university and have access to a photomultiplier tube (try a physics lab), I would give that a try using an ordinary flash inside the bellows. This way you can look at a meter rather than trust your eyes to find even the smallest pinhole light leak.JohnK

Flare problem due to excessive coverage

Another cause of this sort of problem is flare due to the sun or another bright light source out of the composed frame, bouncing light off the bellows and dumping the non-image light on part of the film. Since the lens reverses the image position on film, the upper right of your photo would be lower left on the ground glass - the sun, outside the frame to the upper right could be reflected by the bellows to the lower left area of the GG/film causing fogging. The solution is to use a lens hood, compendium bellows, or a card to prevent sources outside the composed frame from illuminating the lens and reflecting off the interior of the bellows. Michael Gudzinowicz

Finally, as a reward for those who slogged thru all of that, I have one last note - this I discovered today. A friend had an image spoiled by what looked like a light leak - the fogging appeared as a splash of light from the top of the frame. We examined the negative, and it seemed that, perhaps, it was caused by the image of the sun, which was just barely out of the frame. It looked rather as if the image of the sun fell on the beveled edge of the readyload film holder - around the frame, the bevel slopes *in* toward the film. And it looked to me like the image of the sun fell on this bevel, and reflected off and was splashed across the film. Ick. I think the moral of the story is that if the sun is just outside the frame, use a lens hood and adjust it very carefully. Paul Butzi.

Holder not sitting light-tight against camera

I suggest this: once you insert the holder, try wrapping the darkcloth around it and the back, leaving just enough to pull the slide. Or maybe wrap the entire back and holder, clip it shut with clothespins, and pull the slide inside there. It sounds like the holder is not seating light-tight against the camera. I think it's occasional possibly due to moisture changes in the atmosphere causing the wood to warp slightly. David Meiland

Would it be possible to put some black felt where the cutfilm holder rests against the back? Robert Peters

I had a problem with light leaks when I first started in 4 x 5. Do not take the dark slide out until you are ready to shoot. Replace it immediately after you shoot. I ran into my light leak problem by putting just the corner of the dark slide in first. You have to put the slide in perfectly straight, or you get a light leak. Rob

I have old wooden film holders that have been a great deal of trouble with light leaks for the two years or so that I've been trying to use them. I just came back from a trip and this time I kept the dark cloth on the camera during exposures and guess what? No light leaks on any of the film, a first! I thought that the leaks had ocurred in handling the film holders or even carrying them around, but this seems to indicate that the leaks ocurr only when opening and closing the dark slides. Frank Kolwicz

Other possibilities that come to mind are: not getting the holder seated before pulling the dark slide, shifting the holder when pulling the dark slide. Basically anything that might pull the holder away from the camera back. If you routinely shoot straight up, are those more likely to be fogged? The weight of the holder might be pulling it away from the back due to weakened springs. Paul Butzi

Leaking preloaded film systems

Many people have reported problems with light leaks using preloaded systems, especially the kodak readyloads and/or polaroid back. Look at the diagnosis and tips to avoid problems.

Leaks outside of the camera

How and where do you load your holders? Do you wear, perhaps, a wristwatch with a luminescent face? (Yes, I *have* fogged film that way). Paul Butzi

If the fogging happens on the unexposed-but-processed film, try a different lab. If it still shows up, I'd say you're handling it wrong and you'll have to look at your environment (Don Nelson's point about fluorescents being able to fog film after being turned off is correct, in my experience). Pete Bergstrom

Two thoughts: 1) is the box you transport your exposed negative to the film lab in light tight? 2) Are you sure these "blobs" are not processing failures of some kind. I had a roll of 35mm E6 butchered on me last year by a "professional" lab, and some of your blobs look a little like what I had on my roll of film. Either that, or could there be light leaks in the lab somewhere ? Joseph O'Neil

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