dark strip on processed films

[Nathan Potter]

It's hard to invoke camera light leak cause that would produce such a uniform exposed line across the film at that specific location. I'd have to look at the seating of the holder within the back as being intermittent (human error?) since the phenomena is intermittent.

A thin line of light is reaching the film at a consistent point across the film plane. The shading off of the exposure laterally indicates a diffraction pattern exposure. Can't see how that could occur during development. Look for any other possible light leaks in the back assembly. It appears that they might be minor, but present. As another poster has suggested the effect is digital (it's there or it isn't) suggesting human error.

Nate Potter, Washington DC.

[Gem Singer]

Nathan,

I did not invoke anything.

Perhaps i should have worded my suggestion--from the appearance the last picture, the light leak doesn't look like it's coming from a faulty film holder. It's probably coming from the camera.

Look for a bellows leak or a poor fit between the film holder and the back of the camera.

[Preston]

After taking a close look at the color shot, I agree. Paul's test should show if there are any light leaks.

Not long after I got my used Tachihara I experienced some fogging. I waited until I had very dark night, extended the bellows, and, using a small maglite from inside camera I was greeted with what looked like a starry night!

-Preston

[Yan Preston]

The gentleman from the commercial lab that I used (Peak Imaging in Sheffield, England) suggested 'light reflection from the dark slide'. I've ordered a lot of films and will start doing a lot of tests soon. Will keep you all posted. Thanks.

[Yan Preston]

Tests results:
I took the camera in the darkroom, put a head torch in the bellows and confirmed that there's no leak from the lens board or the bellows. However, I noticed that the flexible metal piece on the camera back was quite weak (this is a China made Shenhao, it doesn't have a spring system on the back). When I put the dark slide in and out, if I'm not careful enough, the back will be accidently open a little bit and create a light leak. The solution to this is to squeeze the back and camera body together with my left hand, while the right hand carefully take the dark slide in and out. With this solution I did another 8 sheets of tests. With 4 out of these 8 I applied the new technique, the result had no problem. With the other 4 I did how I usually operate the camera, 2 out of these were fine. The other 2, I purposely created a very obvious gap so the sheets had a vague line and part of the film was fogged.

Somebody else suggested that the gap on the film holder where the dark slide goes in and out might be leaking, I'm unable to confirm on this one yet.

So far, I guess the weak spring and slightly rough operation might be the reason of the leak. However, given the fact that it wasn't consistent before, I can not guarantee this as the absolute cause. I'm going to start shooting normally using the new 'squeezing' technique, if the problem never happens again, I'll say it's cured. Otherwise I may have to change the system. I'll keep you posted.

[Louie Powell]

Well, damn! I've been processing film from a recent trip to California, and one of the negatives has a defect just like you described.

I reloaded and reused that same holder several times during the course of the trip. And the curious thing is that, for some strange reason, I opted to make two negatives of the first two scenes I photographed that morning, and only one of the negatives is flawed.

So it has to be the #1 problem facing LF photographers - dumb, human error.