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Cletus
14-Oct-2012, 07:00
I'm not sure exactly where this should be posted, but since it's showing up on my film, why not here?

I'm noticing on many of my 8x10 negatives there is a consistent pattern of "exposure", right about smack in the middle of some of my negatives. I may try to post a scan of this, but it'll be hard to scan and this description might stand out to someone anyway -

The "light leak" mark, if that's what it is, is NOT related to any particular holder, so eliminates that as far as I can tell. The "mark" is shaped something like a scratch, about 2.5-3" long, with some little random scratch looking marks near one end of the anomaly. The "little marks", concentrated near the "top" of the long mark, are consistent with the camera moving before exposure, after the darkslide has been pulled. Although, when I think about it the "camera moving theory" doesn't make as much sense, as the film holder and camera really shouldn't move relative to each other that way after the holder has been inserted. (???) But than again, if it's a point light source on the bellows, I suppose it could still cause the little marks....I don't know....what about the long one then?

This appears both on negatives exposed outside in bright sun and also inside in very subdued light, using a studio strobe. What perplexes me is that the mark is reasonably consistent from negative to negative in size, shape and intensity and appears just about right in the center of the negative in the "axial" or long direction. If were actually a scratch and not an exposure mark, I might think it was sand in my holder light trap, but again, the mark isn't related to any one holder. Overall, the marks are fairly sharp, indicating that the leak - if that's what it is - would be closer to the back of the camera than the front. It seems to me anyway. The "density" of the mark is fairly high, about medium grey (I don't have a densitometer, so can't provide a number).

Here's something else that really makes me wonder - The same mark(s) also appear on a blank negative - the second frame of the same subject that I thought I had exposed (I do this from time to time). The darkslide was still on the white unexposed side and I don't know whether I forgot to cock the shutter, or it misfired, or what? I must have pulled the darkslide though, when I thought I was making the exposure, otherwise the mark would indicate the "leak" is coming from somewhere other than the camera????? I can't think what I'd be doing in the darkroom, while loading holders that could cause this anomaly to be so consistent in size and location from neg to neg?

Anyway, this is about the best description I can make of what I'm seeing with going into one of my 5,000 word essays - I'm working on being more concise :) - and I am stumped. I don't know how, or what kind of setup I'd need to test my camera for this, as I mildly suspect this must be a "point source" leak coming from somewhere around my camera back, or maybe the bellows near the back of my Sinar F2.

Any thoughts on this? Does this ring a bell with anyone, or sound just like something you've seen before? I'm trying to come up with a plan to test the camera and locate this leak, but coming up short on ideas how to do this.

Cletus
14-Oct-2012, 07:19
Okay, I don't have a scan of a negative showing this, but here's a jpeg of a rough drawing showing the approximate size, shape and unfortunate location of the marks on the negatives. It's obviously not as dense as it appears in this sketch, but not too far off!

Thanks for your advice or ideas...


82047

Gem Singer
14-Oct-2012, 07:33
Phil,

Look for a small opening in, or around the lens board area.

Jim Noel
14-Oct-2012, 07:36
It sounds like a light leak around the lens board, or the front part of the bellows. Check it by removing the back of the camera and placing a dark cloth over it. Turn off the lights and sit inthe dark for 4-5 minutes until your pupils are dilated. Then with your head under the dark cloth, turn on a bright light at the front of the camera.

Cletus
14-Oct-2012, 09:19
Gem / Jim -

Thanks for the ideas and I'll check for that again, but I' not sure this is something coming from the front of the camera. It could be, but it seems to me it wouldn't such a sharp exposure coming from that far away from the film. Wouldn't it be more of a diffuse fog the leak were all the way toward the front of the camera? And I've already done the trick with the lights off. I can do it again, but I haven't figured out how to do it reliably with the back on the camera. I suspect this is coming from someplace closer to the film, but I'll try again and see what I can see.

It's hard to imagine I have a "hole" in a lensboard, or anything in front other than the bellows. And that I haven't been able to spot it???

Gem - It's getting busy for me these days and I'm on the road a lot, but how about another photo outing when I get home and have some time?

Phil

Cletus
14-Oct-2012, 09:27
Oh, another thing on the light leak - If you look at the drawing I attached, you can see that the film is in landscape orientation and the orientation of the mark is also in landscape. If I move the back on the camera to portrait orientation, the mark changes to portrait orientation too. If it were a light leak from inside the camera, how could this be? Wouldn't the exposure pattern from the leak stay in the same orientation, regardless of the position of the film?

I asked this question once a long time ago and got an answer, but now I'll ask it again anyway. I have two Gralab 300 timers in my darkroom, right above the counter where I load my film. My new timer is the plastic model with plastic glowing hands and indices. I'm still wondering if there's any chance this timer glows bright enough to expose ISO400 film like this while I'm loading it into the holders? Or likewise, while I'm tray developing the film.

If this were happening in the darkroom and not in the camera at all, that would answer some strange questions I have in my mind right now. I just can't figure out how the mark can be so consistent in terms of it's location on the film and the general shape and size of it. It's not nearly exactly the same on each negative, but fairly close.

Gem Singer
14-Oct-2012, 09:33
Phil,

A pinhole leak in, or around the lens board area has the same effect as a pin hole lens. It projects a relatively sharp image.

Could be a missing screw somewhere in the front of the camera, or a shutter that is not mounted properly.

The luminescence from a GraLab 300 will not expose film (unless you touch the film directly to the glowing face of the timer).

Call me when you are ready to go out shooting. No more extra long road trips. Took me two days to recover from the last one.

Mark MacKenzie
14-Oct-2012, 09:34
I recently had some marks on some Adox MCC 110 paper that were consistent from sheet to sheet. I thought they were thumbprints from my thumb contaminated with chemicals. I have come to the conclusion that they were a flaw in the paper from the manufacturer. Is it possible your batch of film has a flaw on each sheet? The answer would be to develop a completely unexposed sheet that never even touched your camera.

Jim Jones
14-Oct-2012, 15:48
I've had a variety of odd marks on 35mm film shot and unloaded in very low humidity, but wouldn't expect that problem this time of year in Texas.

E. von Hoegh
15-Oct-2012, 06:51
How are you processing the film?

Cletus
15-Oct-2012, 09:11
E. - I tray process all sheet film, with the emulsion side down (I seem to have better luck with scratches that way) and my trays are probably less than 3' from the Gralab timer I use for processing. That's why I thought it might be coming from the glowing face and hands of the timer, but I've gotten all kinds of response, now and earlier, from people insisting that the timer glow will not affect / fog film. I've been doing my 4x5 this way for quite a while and never noticed this anomaly on 4x5 sheets, so I'm inclined to think this isn't coming from my timer. I guess I'll burn a few sheets of 4x5 at some point to re-test this myself though. I do have a new timer and it glows quite a bit brighter than my old one.

I'm still fairly convinced this is a bellows leak and I don't plan to shoot anymore with this 8x10 until I get a chance to do some (further) light leak testing. The next thing I plan to do, is to set up the camera, extend the bellows with the back on and an empty film holder inserted. I'll stick a darkcloth over the front and look through the front standard, using a strong flashlight to 'scan' all the areas around the back standard and fame where the bellows attach. I figure if I do this while pulling the darkslide in and out, flexing the bellows and moving stuff around, if there's a light leak back there it should show up. I have an extremely powerful flashlight, so if that don't show something, I'll have to go back to the drawing board. Also, on close inspection I can see some repair work around the rear of bellows that I hadn't noticed before and it's duct tape! I plan to order either a new "ecbuyonline" bellows, or a dacron repair kit from B&S whether I find a leak or not.

Even then, the chance of a bellows leak still doesn't go too far in explaining the shape and location of the marks on the film, but it's one more thing to eliminate anyway. Any other ideas on what could be causing something like this, outside of a leak in the camera?

E. von Hoegh
15-Oct-2012, 09:13
E. - I tray process all sheet film, with the emulsion side down (I seem to have better luck with scratches that way) and my trays are probably less than 3' from the Gralab timer I use for processing. That's why I thought it might be coming from the glowing face and hands of the timer, but I've gotten all kinds of response, now and earlier, from people insisting that the timer glow will not affect / fog film. I've been doing my 4x5 this way for quite a while and never noticed this anomaly on 4x5 sheets, so I'm inclined to think this isn't coming from my timer. I guess I'll burn a few sheets of 4x5 at some point to re-test this myself though. I do have a new timer and it glows quite a bit brighter than my old one.

I'm still fairly convinced this is a bellows leak and I don't plan to shoot anymore with this 8x10 until I get a chance to do some (further) light leak testing. The next thing I plan to do, is to set up the camera, extend the bellows with the back on and an empty film holder inserted. I'll stick a darkcloth over the front and look through the front standard, using a strong flashlight to 'scan' all the areas around the back standard and fame where the bellows attach. I figure if I do this while pulling the darkslide in and out, flexing the bellows and moving stuff around, if there's a light leak back there it should show up. I have an extremely powerful flashlight, so if that don't show something, I'll have to go back to the drawing board. Also, on close inspection I can see some repair work around the rear of bellows that I hadn't noticed before and it's duct tape! I plan to order either a new "ecbuyonline" bellows, or a dacron repair kit from B&S whether I find a leak or not.

Even then, the chance of a bellows leak still doesn't go too far in explaining the shape and location of the marks on the film, but it's one more thing to eliminate anyway. Any other ideas on what could be causing something like this, outside of a leak in the camera?

Emulsion side down?? What's in the middle of the bottom of your tray? A mould sprue/release mark?

Gem Singer
15-Oct-2012, 09:51
Scratches on the emulsion side of film are easily seen as clear areas on the film and print as dark areas.

Light leaks show up as dark areas on the negative and print as light areas.

From the description of the problem, it appears to be a light leak. No need to waste a sheet of film.

Extend the bellows all the way. In a darkened room, place a light inside of the bellows. If you can see pinholes of light on the outside of the bellows, you found the leak.

Especially check where the bellows is attached to the front and rear standards.

Cletus
15-Oct-2012, 10:07
Gem -

Yes, this is pretty much what I plan to do when I get home and have some time. Thanks.

E. - The marks on the film do look like scratches, but aren't. It's actual density from exposure, similar to the pattern in the little sketch I posted. Not very good, but gives the general idea. I did think it was scratches at first, but it's definitely in the emulsion. I used to process emulsion up, but ended up with too many scratches from shuffling the film stack during development. It works better for me emulsion side down and my trays are pretty smooth on the bottom. Thanks for the suggestion though.