Mysterious halos on negatives

[komatsu]

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?



Thanks,

Leo

[Andrew O'Neill]

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]

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]

Both lenses stopped down and no rings? weird.

[komatsu]

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]

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]

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]

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]

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]

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