[pure-silver] Re: Fog or Light Leak
- From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
- To: <pure-silver@xxxxxxxxxxxxx>
- Date: Sun, 29 Nov 2009 16:15:15 -0800
----- Original Message -----
From: "Elias Roustom" <elroustom@xxxxxxxxx>
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Sunday, November 29, 2009 11:42 AM
Subject: [pure-silver] Fog or Light Leak
I'm trying to chase down a problem.
Does sheet film that's a past due fog in its packaging?
Delta Pro 100, May 2009. Not kept in fridge.
Or I have a light leak somewhere in my process.
E.
How old is it? Was the package ever opened? The short
answer is that film does fog. It has various things in it to
prevent or slow fogging but the chemical process of
"ripening" that increases sensitivity of the film does
continue very slowly with time despite chemicals added to
supress it. Exposure to high temperatures will accelerate
age fogging as will oxidation where the package has been
opened. Age fog is usually very uniform but can also have a
slightly mottled appearance. The film can be overexposed a
bit to bring the shadows above the fog level or a fog
suppressant like benzotriazole can be added to the
developer. The results of both are similar, a loss of film
speed.
One reason for expiration dates is age fog although
there are other changes with time. Usually expiration dates
are very conservative but it is my impression that modern
film does not last as long as some of the older stuff.
If the fog has definite outlines its probably from
something else.
--
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
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