What kind of light leak is this?

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waileong

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Excuse the grain; this is HP5+ pushed to 3200.

What kind of light leak is this? You can see clearly the image of the backing paper in the frame. You can see the frame numbers. Indeed, all the frames are similarly exposed.

I've had fogging, I've had darkroom accidents, I've even had shutters that leak light.

But I've never seen a roll of film completely and evenly exposed so that the backing paper can be clearly seen-- yet it is not fogged enough and can still render an image!

Any ideas anyone?
 

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Halation is light (mostly IR) passing through film and bouncing back from pressure plate as visible to film light. The dyes stop that from happening. But if there was any moisture/condensation on film back the marks could be made in dyes from backing paper. Thats why I asked if film is properly washed. It could possibly wash off. I'm just guessing here not saying that is definitely the problem.
 
Maybe the film had some issues with moisture from freezing/cooling or packing, making it possible for a transfer from the backing-paper, pre exposure?
 
waileong said:
Don't think so. I've used a lot of hp5+ over the years.
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I'm thinking of 4x5 which has plenty, I assume roll film has it too but I'll stand corrected on that if you are sure.

But you are saying then that there is nothing on the back of the film and that the marks are in the emulsion.
 
What camera are you shooting on? Printing on the backing paper showing through I thought usually occurs because of crummy 'red windows' on your 120 camera.
 
waileong said:
But I've never seen a roll of film completely and evenly exposed so that the backing paper can be clearly seen-- yet it is not fogged enough and can still render an image!

Any ideas anyone?
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I assume that the backing print-though occurs across all frames and out of frame areas at about similar intensity, and that the print-though numbers are offset to the edge enumeration by the length of one spool circumference.

If so, I've seen things like that, mostly on expired or overheated film, but about 20 years ago Ilford had a few bad batches of backing paper that caused similar issues even on fresh film. It is due to chemical interaction of the emulsion with the backing inscription - the ink or its decomposition products fog the film or affect the film sensitizing in some way or other.
 
waileong said:
Hp5+ does not have an anti-halation dye. In any case, what has that got to do with light leak?
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You need to download the techinical pdf from Ilford. You'll see it does have an anti-hation backing that comes off during development. Bottom line is your wrong.:)
 
Just tell folks it was a background special effects projection;)

I've seen examples of this happening to different films. It's the ink from the backing paper. Bummer.

PF
 
Doh - of course a red window leak wouldn't expose all of the ink backings. Somehow I missed that on the first look.

Maybe send an email or PM to Simon Galley over on APUG. He works for Ilford and should sort you out pretty quickly. Is it fresh film or old?
 
Found the answer. It's expired film. Long expired film coupled with cosmic radiation. Or perhaps too many doses of supposedly film-safe x-rays.

Thanks guys!
 
waileong said:
Found the answer. It's expired film. Long expired film coupled with cosmic radiation. Or perhaps too many doses of supposedly film-safe x-rays.
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Not unless you stored (or aircraft transported) that film unwound into a long tape - cosmic radiation and x-rays come from one direction and cannot expose film rolled up into a spool evenly.

As said, it is a issue with the backing number ink - and if the film is long expired, it might even be from the period when Ilford had a issue with these fogging their film...
 
sevo said:
Not unless you stored (or aircraft transported) that film unwound into a long tape - cosmic radiation and x-rays come from one direction and cannot expose film rolled up into a spool evenly.

As said, it is a issue with the backing number ink - and if the film is long expired, it might even be from the period when Ilford had a issue with these fogging their film...
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See http://forum.mflenses.com/rollei-retro-80-120-light-leak-t48361.html for an example.

I'm using a new Mamiya 6 too, coincidentally.
 
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