Re: Three-color gum prints

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From: Gerard NIEMETZKY (gerard@atxstudio.com)
Date: 09/07/00-03:11:56 PM Z

The problem you will have with Wratten 25 is its Spectral transmission. It
is not a problem of prolongation factor in visible light.

To print with dichromated emulsions you need light of wavelength between 350
and 450nm (mainly UV light).

The Wratten 25 filter does not transmit anything under 580nm (and only 12%
at 590nm). So you could expose as long as you want, your emulsion will never
been exposed.

Regards 

-- 
Gerard Niemetzky
http://www.atxstudio.com

From: lva <lva@pamho.net>
Reply-To: alt-photo-process-l@sask.usask.ca
Date: Thu, 07 Sep 2000 20:45 +0200
To: alt-photo-process-l@sask.usask.ca
Subject: Re: Three-color gum prints

>The big disadvantage I see from this approach is the
>radically increased exposure time onto your gum emulsion (due to
>filters sandwiched with the negative).

Shouldn't be that bad. Current exposures range from 90 to 120 seconds. A
Wratten 25 filter would turn that into 12 minutes. Not that bad.

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