Re: large format ortho

Hi:

I use 8x10 ortho to make big negatives. I mostly print cyanotype though.
The key is using a very low contrast developer.

People have had success using a highly diluted print developer - such as
dektol, selectol sprint etc. diluted (10:1 to 30:1).

The ASA of the film is around 6 with these developers.

I find these are still too contrasty with the ortho film I use (kpgraphics
CGP)

A very good low contrast developer formulated specifically for producing
low contrast negatives from ortho film is Dave Soemarko's LC-1 developer

http://members.aol.com/fotodave/Articles/LC-1.html

This developer is not commerically made - you must mix it yourself.

By varying the dilution and mix its possible to control the contrast
effectively.

LC-1 does result in a significant speed loss though - film processed in
LC-1 has an ASA of 1.

This does become an issue with very large format cameras, if your pinhole
is small, the f stop is so small that the expsosure time can stretch to
hours.

You might try seeing how large of a pinhole you can tolerate (and its
fuzziness) before you start shooting 16 x 20

I think an XTOL ascorbic acid based developer at a low pH seems to work
better

See Mytol http://www.jackspcs.com/mytol.htm

Chemical Amount Units

Distilled Water 750 ml
Sodium Sulfite 60 g
Sodium Metaborate 4 g
Sodium Ascorbate 13 g
Phenidone 0.15 g
Sodium Metabisulfite 3 g
Distilled water to make 1000 ml

This formula mixed without the alkali agent (Sodium Metaborate) may work better.

I also find that pre-flashing the film at an exposure just less than
something that would fog the film extends the range and sensitivity of
the film.

Testing with a Stouffer step tablet I'm able to get an 18 step negative.
Using a similar developer to Mytol and preflashing the film.

Gord

On Fri, 1 Nov 2002, Tim Midkiff wrote:

> Hello all,
>
> Does anyone have firsthand experience using large format ortho film,
> 16x20, in camera for gum prints? I've been doing a few the hard way,
> making the first exposure, then making a high density neg then making
> the gum prints. any ideas or suggestions, etc would be greatly
> welcomed!!!
>
> thanks, tim
>
>
>
>
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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 Fri Nov 1 12:32:46 2002