Re: filmscanners: which space?

["Karl Schulmeisters" <karlsch@earthlink.net>]

CMYK is not a reduced color space compared to RGB.  Printer CMYK is.  But
that is because the color space of the inks is more reduced.  In essence,
this isn't any different than manipulating The Zone System - ie where the
dynamic range of paper is less than the dynamic range of film, which in turn
is less than the dynamic range of our eyes.

Maris Lidaka wrote:

<The point is that yes, there will be damage and loss without question but,
at least for me, there are times when the benefits of being able to adjust
in CMYK outweigh these damages.>

Sure, I completely agree.  The key though, just like with the Zone System is
to understand what is going on.


----- Original Message -----
From: <TREVITHO@aol.com>
To: <filmscanners@halftone.co.uk>
Sent: Sunday, May 27, 2001 12:34 AM
Subject: Re: filmscanners: which space?


>
>
> Dear Karl
>
> As CMYK is a much reduced colour space compared to RGB I would have
thought
> that made it exactly the case. The true test would be to make multiple
> conversions from RGB to CMYK and back and see if quality suffered, which
of
> course it does.
>
> The real test would be to make the conversion several times in different
> programmes.
>
> R=25%, G=15%, B=10% converts to:-
>
> QUARK           C25 M50 Y65     K64
> PAGEMAKER   C56 M74 Y83 K65
> FREEHAND        C75 M85 Y90
> PHOTOSHOP   C41 M62 Y69 K70
>
> It all depends on your standards. For LVT output you can't even make one
CMYK
> to RGB conversion without noticing adverse quality; for web use you can
> probably get away with several.
>
>
>
>
> In a message dated 26/5/01 8:29:01 am, karlsch@earthlink.net writes:
>
> << That's not exactly the case.  What is the case is that a particular
Hue,
>
> Intensity value - what our eyes perceive as a unique 'color value' can be
>
> rendered with multiple combinations of RGB.  The same is not true for CYMK
>
>
> So when you map from RGB into ANY color space, you essentially lose some
>
> information.  Namely you lose the mapping back to the original value
>
> settings.  That doesn't mean you can't get back to an RGB triplet that
will
>
> look the same, but it does mean that say if you had set the RGB triplet
>
> value to Rx,Gy,Bz then mapped to CYMK and you went back, Rx',Gy',Bz' might
>
> not have
>
> x=x',y=y',z=z'.
>
>
> This matters because you then can't just 'undo' any filtering you did
prior
>
> to the mapping.  Other color spaces have unique tuplet values.  This has
to
>
> do with the fact that in CYMK, intensity is mapped into the gray-scale K,
>
> whereas in RGB, intensity is a function of the particulare RGB values. >>
>
>
>
> Bob Croxford
> Cornwall
> England
>
> www.atmosphere.co.uk