Re: expiration dates on film boxes

From: Richard Knoppow <dickburk@ix.netcom.com>
Subject: Re: expiration dates on film boxes
Date: Thu, 13 Oct 2005 13:12:51 -0700

> I have recently been using up some 4x5 film that is probably at
> least 15 years old. Some shows some fog but some does not. The fog
> is cured by adding a little bromide to the developer. The main
> change in most film is the accumulation of fog. While this has a
> practical effect of lowering speed (as does adding bromide or
> benzotriazole) contrast seems not to change too much and I generally
> give more exposure than the ISO speed calls for anyway.

One must distinguish developer fog and emulsion fog. Age-related fog
is emulsion fog, which reacts with developer much like lightly exposed
grains. Trying to salvage those emulsions by adding bromide or
benzotriazole is usually a wate of effort, possibly except very early
point in the fogging.

Use of restrainers or antifoggants do not necessarily come with speed
loss. Studies by Hillson of Kodak HArrow in 1970s showed that
simultaneous addition of antifoggants and powerful development
accelerator could enhance discrimination of exposed and unexposed
grains. He added 5-methylbenzotriazole and CD-2 to DX-80 developer,
among other conditions. He also used Plus-X in modified D-19 and D-8.
In those cases he demonstrated significant speed increase by adding
5-MBTA. He proposed that the enhanced discrimination could be achieved
by prolonging induction period and accelerating rapid development
phase at the same time.

The results are very interesting, but I am not sure about the
completeness of the proposed mechanism, in light of more recent
results. I am also not sure about the extent it is applicable to good
pictorial b&w film developers. (Good pictorial FILM developers are
designed to develop grains in parallel development mode, but D-19 is
quite far from this mode of development.)

Anyway, I just wanted to point out that addition of antifoggants does
not necessrily entail in loss of speed. 5MBTA is more powerful
antifoggant than usual benzotriazole. (Unsubstituted benzotriazole is
too weak to be effective in developers containing p-pd derivatives.)

> BTW, I am not enthusiastic about development by
> inspection.

Agreed. Development by inspection was the common practice before
accurate thermometer and light meter were easily accessible to
photographers.

> Overexposed negatives are not much of a problem because modern film
> has tremendous overexposure latitude but the ISO method gives just
> about the minimum exposure for reasonable shadow detail so there is
> very little latitude on the underexposure side.

I have a paper describing the calibration of Weston incident meter,
and another paper describing the rationale behind the change in ASA
standard of negative film speed. Having read them, I understand that
they made effort to make a scientifically sound industrial standard,
but at the same time, there is no one calibration standard that works
for all applications.
Received on Fri Oct 14 01:12:36 2005