Re: Reversal processing for enlarged negatives

From: Liam Lawless <liam.lawless@blueyonder.co.uk>
Subject: Re: Reversal processing for enlarged negatives
Date: Thu, 25 Mar 2004 03:16:20 +0000

> My guess is that it may be due to your not
> using a black (or yellow/orange/red) card under the film - for exposure
> under the enlarger as well as flashing.

I don't know about your film but my lith films have quite dense base
dye until the material is processed. The reflected light has to go
through the base twice. Also, silver halide crystals are quite dense
to specular light, and this is the reason I suggested to flash the
film from both sides to expose large grains, which are to be bleached
out.

> I'm slightly confused by Ryuji's suggestion of using KRST as a
> redeveloper, if I've understood him right. In toning experiments many
> years ago I did try redeveloping bleached prints with selenium
> (home-make Kodak T-56, not KRST... or is selenium T-55?) and I seem to
> remember that stock strength solution would eventually yield a soft,
> brownish image if allowed long enough to do so (a very long time!), but
> I can't imagine it being any use in reversal, other than by toning to
> strengthen an otherwise finished neg. On the other hand, it was a very
> long time ago and I don't remember if I was using some weird bleach, so
> maybe I'm wrong... in which case apologies to Ryuji. Has anyone tried
> this?

I suggest to try KRST in place of fogging and redevelopment as a way
to ensure redevelopment of all silver halide crystals. Using KRST will
redevelop more crystals than room light exposure and ordinary
redevelopment. This will keep more fine grains and contribute to Dmax
as well as reduced granularity. But denser result may have to be
compensated for by more initial exposure (imagewise, flash or both).

> Ryuji's other suggestion of flashing from the backside as well sounds
> kind of sensible, but really isn't necessary for the simple reason that
> the flash time is determined by test strip and if the film ain't getting
> enough light we can give it more time.

I'm saying that the crystals near the film surface may receive enough
light but crystals near the base may not be flashed enough. In that
case, more of bigger grains remain in the final image leading to
greater granularity.

> As for different films and developers, I found lith film almost perfect
> for reversing, presumably because of its high contrast. I didn't try

I'm saying that there are many different kinds of "lith" films, some
of which are more similar to line film. Though people tend to mix them
up and put in a "graphic art material" category, these are really
different emulsions in terms of desired photographic properties.

Lith films are used to make halftone images etc. from continuous tone
original, and highest possible contrast is desired. In classic lith
films processed in hydroquinone-only developers, resolution is not
optimal because of infectious development, which is the best way to
achieve high gamma and Dmax. Disadvantage is that this type of
processing is not very suitable to machine operated volume processing,
and it is more difficult to make the whole system environmentally
friendly (cadmium, hydroquinne).

Other kinds of lith films, that are more similar to line films, are
used to photograph originals that are already in black-or-white but
often contains fine details, so higher contrast is desired but high
resolution is also important. This type of processing is very machine
friendly, and there are ways to avoid cadmium and hydroquinone. Many
of later "lith" films are actually of this type.

Of course there are rather radical binary classification and there are
many crosses of them, but speaking of "lith film" as if there were
only one kind of lith film is very misleading.

--
Ryuji Suzuki
"All the truth in the world adds up to one big lie." (Bob Dylan 2000)