Identifying light leak

[seandooley]

Hello everyone,
I'm hoping you can help me identify the source of light leaks I'm getting, which seem to be lens specific. At the bottom of the frame in every picture I take I get two light leaks, about a third and two thirds of the way along the bottom edge of the negative.

Here is a picture showing the problem:

http://www.seandooley.com/lightleaks.jpg

This only happens with one of my lenses - a 90mm Super Angulon. I've tried taking out dark slides with the shutter in both the cocked and the fired states (but not firing the shutter) and there are no light leaks, so it isn't the bellows or the camera. It only happens with one lens so isn't my film handling or loading techniques, or the camera back. It seems to be unique to this lens.

Turning the lens up the other way on the board makes no difference - the leaks still appear at the bottom of the frame. Light conditions make no difference - sunny skies, overcast, dark rooms with individual light sources - all end up with the same leaks in the same position. The lens is positioned centrally over the back.

Any suggestion on what this could be, or what further steps I could take to identify the problem?

Thanks,
Sean

[C. D. Keth]

I assume it happens with all of your holders, not just one? I would suspect a couple spots inside the rear of the camera that are shiny from wear or a couple bits of shiny hardware exposed and that it takes the angle of light provided by that lens to make it show up. Remove the back, focus to around 90mm without a lens and shine a flashlight from the lens position and see if anything shines.

[lenser]

Sean, you don't mention what camera this is on. It looks for all the world like it may be an artifact of actually photographing the front rails of a flat bed camera like a Zone VI or Crown Graphic or many others. I get that all the time on my zone VI and my 58mm XL if I don't configure the camera correctly to allow for this possibility. I would get it with my 90mm Caltar if I put the lens in a "fall" position without dropping the bed or otherwise configuring the camera to prevent the rails from appearing in the frame.

I'm not saying that you problem isn't a light leak, but the fact that it does not occur with the other lenses, and the perfect placement on the artifacts in every exposure, leads me to think it's how you set up the camera, rather than a leak.

[C. D. Keth]

Sean, you don't mention what camera this is on. It looks for all the world like it may be an artifact of actually photographing the front rails of a flat bed camera like a Zone VI or Crown Graphic or many others. I get that all the time on my zone VI and my 58mm XL if I don't configure the camera correctly to allow for this possibility. I would get it with my 90mm Caltar if I put the lens in a "fall" position without dropping the bed or otherwise configuring the camera to prevent the rails from appearing in the frame.

I'm not saying that you problem isn't a light leak, but the fact that it does not occur with the other lenses, and the perfect placement on the artifacts in every exposure, leads me to think it's how you set up the camera, rather that a leak.

Good call and a distinct possibility. The rails themselves or flare from shiny camera rails just out of frame.

[RawheaD]

I was going to chime in to comment the same; the fact that it's only the wideangle makes that hypothesis plausible. I bet if you used a 75mm, it'd look like this:
85606

LOL

[lenser]

Christopher, It's actually an easy call for me as I blunder into that situation almost every time I set up the camera and use my widest lenses. I think I need a small flashing sign on the back of camera that states "Did you remember drop the bed this time, Dummy?"

[seandooley]

How embarrassing. The camera - a speed graphic - and lens are relatively new to me and I'm only just learning the differences compared to the monorail that I've always used in the past. I think you hit the nail on the head, lenser - it never even occurred to me that I would need to drop the bed. Not a light leak at all but the tips of the rails in the picture. Thanks everyone, problem solved!

[lenser]

Sean,

Glad it was such a simple fix and for Pete's sake, don't be embarrassed. I'm completely serious that I all too often put my 58mm XL on the camera and start to set up the shot without giving a thought to the need to set the body up in a radically different geometry to keep those rails out of frame. All of a sudden I remember and it's always a Homer Simpson moment and another few minutes to reorganize before I'm actually good to go.

Enjoy that Speed Graphic. Other than the lack of a bag bellows for extreme movements, it is one heck of a camera.