[alt-photo] Re: Development By Inspection Methods

[Richard Knoppow]

----- Original Message ----- 
From: "Francesco Fragomeni" <fdfragomeni at gmail.com>
To: "The alternative photographic processes mailing list" 
<alt-photo-process-list at lists.altphotolist.org>
Sent: Wednesday, March 07, 2012 7:47 PM
Subject: [alt-photo] Re: Development By Inspection Methods


> Thanks Ken,
>
> I've found a few things written about Pinacryptol Yellow 
> and Pinacryptol
> Green that I had not previously seen. They echo your 
> experience with the
> desensitizer reducing the speed of the film significantly. 
> I've also found
> reports that it may not work or be effective with modern 
> faster films. I
> was hoping that these desensitizers would be more useful 
> then they
> apparently are and I suppose that explains why they are 
> nearly impossible
> to get a hold of these days. If there was anything magical 
> about them
> they'd probably be in use today.
>
> I'm very interested in what I'll be able to do with the 
> green safelight
> technique (minus the desensitizer). I use 100 and 400 
> speed films. My only
> concern is whether or not 400 ISO film will be 
> dramatically more apt to fog
> using the technique. I understand that the green safelight 
> is only on for a
> few seconds at a time and kept at a safe distance and I 
> get that the film
> desensitizes as it develops but I' still concerned that 
> faster film will
> fog. Anyone have any experience developing 400 ISO film 
> this way? Are there
> any problems with it?
>
> -Francesco

    FWIW, the theory behind using the green safelight is 
that its peaked at the color the eye is most sensitive to 
when dark adapted. As a result it can be dimmer than light 
of another color for the same visual brightness.  Also, 
until recently, panchromatic films had a dip in the 
sensitivity in the green. Have a look at the published 
spectral sensitivity curves for film to see what I mean. Its 
slight but there.  More modern pan films like T-Max and 
other tabular grain films tend to have more uniform 
sensitivity.  Also, most developers act as desensitizers so 
that after half the developing time the film has lost much 
of its sensitivity and so the light is less likely to cause 
fogging. Nonetheless, the green safelight can be used for 
only a few seconds. I've found that judging densities is 
difficult especially since the undeveloped halide results in 
the film looking quite different from the way it does after 
fixing.
    I think there are circumstances where development by 
inspection may be necessary but film is very uniform so that 
development by time and temperature can result in very 
predictable results provided some care is used so I think 
development by inspection should be reserved for those times 
where there is something unusual that makes it necessary.

--
Richard Knoppow
Los Angeles, CA, USA
dickburk at ix.netcom.com