Light Leaks - what could it be?

[Claudius]

Hiya,

I have two distinctively different light leaks happening frequently, but not always. I am shooting with a 8x10 Sinar with metering back and plastic fidelity elite holders.
One (as in the b&w example) starts about once cm in from the side with a fairly hard edge, slowly fading out. It occurs on the side of the dark slide insert.
The other one is two fairly sharp edged light lines few mm and about one cm in from the edge with a less exposed area in between. This one occurs on the side of the flap.
Having numbered all holders, I know for sure that either problem is not linked to a specific holder (yet it might be the same fault at several).
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Because of the fairly sharp edges, I'd blame something close to the film. Yet I am not sure where it could happen. I tried a lot but with out success... The light trap at the dark slide entrance? Between camera and holder? Is it handling (wrong inserting of the dark slide, transport, etc)? Any help appreciated!

best,
Claudius

[Ken Lee]

Do you hold the camera back against the film-holder (with your thumb) whenever inserting or removing the dark slide ?

Even with a Sinar and its hinged back, it's easy for the back to come ever-so-slightly loose during those crucial moments and allow a small amount of light to "fog" a side portion of the film. I've noticed that the larger the film-holdef the easier this can happen, perhaps because more energy is required (and more potential torque or leverage) to move larger slides.

You might also find it helpful to wax your dark slides now and then (just the parts which slide along the inner rails). The more easily they slide, the less potential to yank on them or move them at an angle.

[Peter Mounier]

I was a little puzzled about how the B&W image could have a dark anomaly on the edge, and be described as a light leak. The darker edge would indicate less exposure than the rest of the neg, and thus, not a light leak. The color image has a brighter edge, which could be a light leak. I don't think so though, because if you apply a curve to the image to see the details of the anomaly, it looks more like a processing error. I've attached a crop of the image to more graphically show the edge.

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[Claudius]

Thank you for your replies!

I have to admit I did not hold the back while pulling the darkslide. Yet the springs of my back are quite firm and the slides move easily. I will make sure I will do that the next couple of times. (or have the dark cloth over the back)

Processing error? Interesting, I haven't considered that yet. I will go through all photos again today - I get b&w and colour done at different labs, so it should be fairly easy to see if it only occurs with the colour ones. What is the charateristic look of processing errors? There are so many jpg artifacts on your version Peter that I couldn't see anything (plus I don't know what to look for). I applied quite some curves on the original, here it is:

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@Peter: the light leak at the b&w starts about one centimeter in. Thus, the dark area all the way at the edge is without light leak, the fogging only starts a bit in, around the left lights of the white van.

[IanG]

Definitelyn looks like process marks, insufficient agitation as well as perhaps slightly too little chemistry.

Ian

[Claudius]

Thanks Ian! What puzzles me is that I would expect a more irregular effect if it is a processing problem? The lines are perfectly parallel to the edge of the negative!
It's C41 machine developed in the best lab in the area. Of course, the heydays of film are long over and lab might not be anymore what it was 10 years ago.

[Sevo]

It is what happens when the edge of the film is outside the developer. Do you use a unusual film size just a bit over one of the regular sizes?

Historically I'd have said 4x5" in a 9x12cm country, but I don't think any of the latter still exists. But the underdeveloped upper edge on 4x5" sheets used to be a occasional problem in Germany when 9x12cm still was the local main format, some thirty or forty years ago, as miser labs ran their developer volume so low that it barely avoided getting into the 9x12 frame. I don't however think there ever was a similar issue between 8x10" and 18x24cm - both formats were rare enough that the labs had to make sure their tanks had the proper filling level...

[Claudius]

That makes sense. I double checked all negatives I got developed at the same time as the above example and they have identical marks. Time to have a serious discussion with the lab. (it wouldn't be the only issue I have with the lab! They also clamp the negatives to far in, leaving marks in the image area)

[Peter Mounier]

@Peter: the light leak at the b&w starts about one centimeter in. Thus, the dark area all the way at the edge is without light leak, the fogging only starts a bit in, around the left lights of the white van.

Yes, I noticed that. And it doesn't extend all the way down or up as it does in the color shot. Definitely looks more like a light leak than the color shot. I don't have a plausible answer for that one.