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

[Tom Kershaw]

Henry,

Thanks for your response. The issue of the red exposure and film type 
had somehow escaped my consideration.

Tom

Henry Rattle wrote:
> 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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