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komatsu
24-Apr-2015, 08:00
Hi all. I've recently shot two images on 8x10, wide open, utilising a coated 12 inch Dagor and a Fujinon L 300mm. On both shots there appears to be a halo with an even curve which stops at the margins of the holder - so it must be an "in camera" event. I process using an Paterson Orbital.

Anyone have an idea what the problem could be?

132881

Thanks,

Leo

Andrew O'Neill
24-Apr-2015, 08:30
And the halo appears very similar on both sheets? I've never seen anything like this but it sounds like in-camera issue. Have you checked for a leak?

komatsu
24-Apr-2015, 08:39
Hi Andrew. Thanks for your reply. Yes the effect is similar but not identical. As I have absolutely no idea what a bellows leak looks like I wanted to see if anyone regonized this as one before I burned a few sheets finding out.

BTW: I shot the same shot stopped down and there were no rings....

Leo

Andrew O'Neill
24-Apr-2015, 12:33
Both lenses stopped down and no rings? weird.

komatsu
24-Apr-2015, 12:40
You're telling me. I'd assumed a bellows leak would not be so defined. But there's a chance that a leak didn't show up on the other negs by chance... I'll try some tests.

Thanks for your interest!

JoeV
24-Apr-2015, 12:50
Internal reflection from the lens mount that the lens board mounts to? When stopped down, light misses this shiny surface, but when wide open it hits it and gets reflected? Just a SWAG.

~Joe

komatsu
24-Apr-2015, 13:24
You know Joe, both those lenses do have shorter rear barrels than a regular plasmat - so it actually does hold water to an extent. But would reflections project such clearly defined circles? I'm going to have a poke around inside the camera.

Thanks,

Leo

Doremus Scudder
25-Apr-2015, 01:20
This is a light leak of some kind. I'm putting my money on a leak near/at the back of the camera, filmholders not seating correctly in the back or (more likely) operator error unseating the camera back a bit when pulling/re-inserting the darkslide.

It's easy to check for camera light leaks; just stick a light bulb inside the camera in a darkened room and look at the camera from all angles. Check to make sure your holders are seating properly. When pulling or inserting the darkslide, pinch the camera back to the camera body with your free hand so you don't pull the spring back away from the camera and let light in.

Best,

Doremus

komatsu
25-Apr-2015, 03:14
Thanks Doremus, that's some useful information. "Operator Error" is my middle name, so you might be right. I'm curious though: do you know from experience if film holder movement looks like this?

Thanks,

Leo

Doremus Scudder
25-Apr-2015, 08:27
Thanks Doremus, that's some useful information. "Operator Error" is my middle name, so you might be right. I'm curious though: do you know from experience if film holder movement looks like this?

Thanks,

Leo

Leo,

If you mean does pulling the filmholder away from the back when pulling/inserting the darkslide, then, yes, I do know from experience what that looks like and it looks very much like the photo you posted. That said, your light strike is nearer the bottom of the holder, so it may also be something else. Just trying to give you some places to look.

Best,

Doremus

komatsu
25-Apr-2015, 09:45
Thanks Doremus

I think your answer is very plausible. It would explain why the circles are so uniform - I'm glad you mentioned that you've seen something similar. I'm going to take more care in future - and check that there are no foreign objects behind the ground-glass edges.

All the best!

Leo

komatsu
24-Oct-2015, 10:36
Just a quick note to anyone stumbling across this thread one day: those mysterious halos on my negatives were actually produced by the Paterson Orbital Colour Print Processor I use to develop my 8x10's. It turns out that in stronger light they can benefit from having their light traps painted in flat black.

John Olsen
25-Oct-2015, 15:24
Internal reflection from the lens mount that the lens board mounts to? When stopped down, light misses this shiny surface, but when wide open it hits it and gets reflected? Just a SWAG.

~Joe

Joe's idea sounds good to me. A light leak in the bellows might be more of a spray of light, whereas a partly unseated film holder should not made a circular pattern. How about wrapping something black and nonreflective around any edge like that which Joe describes? Of course if there is no edge like that, you do have mystery. Good luck.

Jmarmck
25-Oct-2015, 15:40
May not have anything to do with it but are the rings from the same holder?

Bruce Watson
25-Oct-2015, 17:57
Anyone have an idea what the problem could be?

That doesn't look like an "in camera" event to me. Darker on the outside edges of the negative... looks like a processing error. Something like surge marks? -- where the outside is seeing more agitation than the middle. Could be that the film didn't go into the developer evenly and quickly -- like the center bowed up and out of the solution right at the start for a few seconds maybe. IDK, but those first few seconds in the developer are critical, and screw ups getting the sheet fully immersed can look like these. At least, my old screw ups getting the sheet fully immersed looked like these. :(

But I've never seen a Patterson Orbital processor before, maybe that's impossible. But stranger things have happened processing sheet film...

Andrew O'Neill
25-Oct-2015, 18:18
BTW: I shot the same shot stopped down and there were no rings....


I don't think it's a processing error as he said that stopped down resulted in no rings.

Doremus Scudder
26-Oct-2015, 02:33
Just a quick note to anyone stumbling across this thread one day: those mysterious halos on my negatives were actually produced by the Paterson Orbital Colour Print Processor I use to develop my 8x10's. It turns out that in stronger light they can benefit from having their light traps painted in flat black.

Did anyone posting after komatsu (the OP) posted this actually bother to read it? The problem seems to have been found and solved.

BTW, it turns out that it's a lot like an in-camera light-strike even though it was the processor, not the camera.

Doremus

Bruce Watson
26-Oct-2015, 06:05
I don't think it's a processing error as he said that stopped down resulted in no rings.

I just skimmed the thread since all the posts where saying more or less the same thing. Missed that one. And I also missed the OPs post #13, where he says: "those mysterious halos on my negatives were actually produced by the Paterson Orbital Colour Print Processor I use to develop my 8x10's. It turns out that in stronger light they can benefit from having their light traps painted in flat black."

Time to quit posting maybe. Oh well...