[alt-photo] Re: From colour transparency to black & white separation negatives for contact printing?

[Henry Rattle]

I've only done this once, nearly 30 years ago...

It makes sense to start from a transparency because you get negatives
directly in one step. I exposed Kodak Plus-X negatives through red, green
and blue Kodak filters (almost certainly no.29 red, no 61 green and 47B
blue). I think it was important to use panchromatic film simply because of
the exposure through the red filter which would presumably not have
registered on ortho film.

There are some very helpful notes on this in William Crawford's wonderful
"Keepers of Light" pages 230-233, including some suggestions for exposure
and development times. Let me know offline if you can't find this and I'll
copy them for you.

Best wishes

Henry


On 31/03/2010 16:30, "Tom Kershaw" <tom at tomkershaw.com> wrote:

> First post to the new list:
> 
> If one wished to produce separation negatives (e.g. for colour gum
> dichromate printing) from an in-camera original transparency in the
> darkroom are any suggestions forthcoming as to an effective procedure?
> Firstly, are there any advantages to be gained by using an
> orthochromatic film (e.g. ILFORD Ortho or Adox Ortho 25) aside from the
> ability to work in safelight conditions?
> 
> Here in the United Kingdom, Fomapan 100 is to the best of my knowledge
> the least expensive film available while still apparently maintaining
> reasonable manufacturing quality control. Has anyone on this list used
> the Foma film for the purposes of making separations? In terms of
> technique, I would assume the use of enlarger filtration controls to
> create red, green, blue tinted projections to be used for cyan, magenta,
> and yellow (approximate) layers in the print. Although I don¹t have the
> reference to hand, I recall ŒDK-50¹ has been suggested as a film
> developer for separations perhaps due to its supposed high contrast
> results. Any suggestions on starting points for relative exposure and
> development between the negatives?
> 
> Tom Kershaw
> 
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