Hi,
I am old book on the colour printing:
Livre d'origine dans un état impeccable d'Alcide Ducos Du
Hauron "La Photographie des Couleurs" et les découvertes de Louis Ducos Du
Hauron suivi d'un manuel pratique, collection A L Guyot
Le livre
d'origine dans un état impeccable " La Photographie des Couleurs" par
impressions pigmentaires superposées, procédé détaillé d'impression au charbon
en plusieurs couleurs superposées pour photographes amateurs et professionnels
de Léon Vidal, Editeur Charles Mendel
Le livre d'origine dans un état
impeccable " Traité Pratique de la Photographie des Couleurs" par L Dugardin
Editeur Société Int de la Photographie des Couleurs
Philippe Atelier
Noir de Faire http://www.photographieaucharbon.net
----- Original Message -----
Sent: Thursday, November 20, 2008 7:52
PM
Subject: separations for gum
printing
All, This recent discussion on tricolor gum printing
sparked my interest. My printing times are about the same with all colors, but
perhaps I compensate with development time, these two variables are related.
But that is not what I wanted to discuss. Mostly everybody agrees that B
channel (in the RGB color space) intended for yellow printing always requires
a different curve then RG channels. This is also my observation and practice.
The B channel is almost always much 'flatter" then oher channels and requires
a more pronounced curvature. Quite frequently I do not have enough definition
in the B channel to get enough contrast resulting in prints with overall
yellow cast. Since CMYK space and separations are intended for printmaking,
which is what we do in gum I started making CMY separations with K set to
zero. There is a visual difference on how the pictures look on screen in these
two color spaces (anyone interested should try to toggle between spaces in
Photosop) and also how the Y separation looks compared to B channnel in
RGB color space. It also seems like the colors are less muddy. I have only
done a few pictures so far, but I want to see if anybody is doing different
methods of generating separations for tricolor gums. Marek
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