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From: Gerhard Fuernkranz <nospam...@gmx.de>
Newsgroups: sci.engr.color
Subject: Re: Chromaticities of digital photo-exposer
Date: Fri, 30 Jan 2004 00:31:57 +0100
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Timo Autiokari schrieb:

> So, are the Frontiers native CMY devices? I had the understanding that
> they use lasers in the RGB space.

Timo,

basically it is NOT the laser light, which you will see, when you look at the 
resulting prints. What I want to say is, the resulting medium which comes out 
of the printer is undoubteldly a *reflective print*, and it surely uses cyan, 
magenta and yellow forming dyes and subtractive color mixing (as Tom already 
explained). The lasers just expose the photo paper.

The lasers, which expose the photo paper, are of course red, green and blue.

But you MUST NOT treat these red, green and blue lasers as a "classical" 
additive RGB color space. In fact, the blue laser rather represents the yellow 
channel, the green laser the magenta channel, and the red laser the cyan 
channel of the resulting print. Furthermore, a negative image is required to 
expose photo paper, i.e. the lasers need to project a negative image on the 
photo paper -- bright laser light will result in high densities, i.e. dark 
colors on the print.

Concerning the workflow, IMO the color space of the RGB image you send to the 
lab for printing is not at all the color space of the RGB lasers which expose 
the photo paper, but just an RGB working space (maybe sRGB or similar?). Given 
the large gamut of digitally printed photos (see Tom's previous posting), I 
would not be surprised, if this RGB working space would be a non-neglectable 
limiting factor for the overall gamut in the workflow.

Regards,
Gerhard