Re: umm (ortho-litho development)

Hi:

I realize this. LC-1 was formulated to produce enlarged copy negatives in the darkroom where
the speed of the film is not critical.

LC-1 reduces the contrast of orhto film by lowering the pH of the developer to the point that it
retards the action of the developer. negative processed in lc-1 have the brown discoloration
typical of an underdeveloped negative.

Lc-1 lowers the contrast by retarding the action of the developer by lowering the pH. The
activity of a developer decreases as the pH of the solution decreases.

The "other" way of producing continuous tone negative from ortho film is to use a highly diluted
developer like Dektol or D-76 T 1:10 or greater. This works by the developer action being
limited by exhaustion (the loss of the developers reduction potential). The developer loses its
activity quickly as the film is being developed resulting in a under-developed low-contrast
image.

The problem with dilute developers are they are not as consistent as LC-1 and are still slightly
more contrasty. Dilute developers are a little faster than LC-1. Diluted Dektol can be used
with orhto with a rating of ASA 6 - but the contrast is much higher.

Gord

On Tue, Mar 05, 2002 at 04:44:01AM -0800, George L Smyth wrote:
> Date: Tue, 05 Mar 2002 04:44:01 -0800 (PST)
> From: George L Smyth <glsmyth@yahoo.com>
> Subject: Re: [pinhole-discussion] umm (ortho-litho development)
> To: pinhole-discussion@pinhole.com
>
> Gord -
>
> It also probably has a fair amount to do with the developer. Many developers
> of this type will result in a lessened film speed. It's just the cost of doing
> business.
>
> Cheers -
>
> george
>
>
>
> --- "Gordon J. Holtslander" <holtsg@duke.usask.ca> wrote:
> >
> > Hi:
> >
> > It seems that rating the film at 1 ASA compensates for reciprocity. I'm
> > not sure of the F-stop of the 12x18- its not my camera. We usually get a
> > good estimate of the pinhole diamter using a loup and a fine ruler
> > graduated in .5 mm From that we calculate the f-stop based on the focal
> > length. We use a light-meter to get an exposure base.
> >
> > It gets good negatives from exposures in the range of 5 min to an hour.
> > Never had an exposure of less than 5 minutes with this film and LC-1
> >
> > Gord
> >
> > On Mon, 4 Mar 2002, John Yeo wrote:
> >
> > >
> > > > I use LC-1 and ortho film too. Its very good. However it is slow. An
> > > ASA of 1. I've used a
> > > > 12 X 18 camera. It ended up having an f stop in the range 0f 300. This
> > > translates to an
> > > > exposure of an hour on a bright sunny day for one picture.
> > >
> > > How does that work? For a sunny day exposure with ASA 1, you would have 1
> > > sec @ f/16. f/360 is 9 stops away from f/16, so your exposure should be
> > > about 8.5 min...
> > >
> > > Or is it because of reciprocity failure that you are getting exposures of
> > an
> > > hour?
> > >
> > > John
> > >
> > >
> > > _______________________________________________
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> >
> > ---------------------------------------------------------
> > Gordon J. Holtslander Dept. of Biology
> > holtsg@duke.usask.ca 112 Science Place
> > http://duke.usask.ca/~holtsg University of Saskatchewan
> > Tel (306) 966-4433 Saskatoon, Saskatchewan
> > Fax (306) 966-4461 Canada S7N 5E2
> > ---------------------------------------------------------
> >
> >
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Received on Tue Mar 5 11:08:14 2002