Re: Rel vs Abs proofs
Re: Rel vs Abs proofs
- Subject: Re: Rel vs Abs proofs
- From: Roger Breton <email@hidden>
- Date: Wed, 11 Oct 2006 21:02:05 -0400
Graeme,
> It's hard to understand what you're saying here. A RelCol rendering will
> never match absolutely,
Completely agree. Part of the point I was trying to raise yesterday night
was the fact that, despite it not being absolute (by definition, it is not
supposed to be absolute), most people I talked, openly or not, expect a
RelCol rendering to be matched absolutely -- they don't really understand
the difference. So that, if I create a RelCol proof and turn that to a
printer, the appearance of color I expect the printer to match is that of
the color on the proof, never mind how that proof was arrived at or what
twist the press will have to take to match its appearance. I think that's a
widespread belief in the industry. Now, it's very possible that a printer
would still able to match my proof in an absolute fashion (pardon my playing
with the semantics of the term), albeit at the expenses of certain tones in
the proof. Certain tones will match better than others. That's the usual
compromise. Let's take the case of skintones for argument sake, say on a
substrate having CIELab 89, 0, 4. If proofed relatively, my experience has
showed me that (maybe wrongly), in AbsCol rendering, the appearance of those
tones will become tainted yellow, to reflect the hue of the media white
point. BUT, when those tones are served in a RelCol rendering, I like to
think that they then shift towards red, if not magenta. The net result of
this, in my view, is to distort the expectation of these tones in an
artifical way. Furthermore, as a result of this shift, in order to match the
proof absolutely (because I'm convinced that this is still the client's
expectation), even though we're talking about a relCol proof, the press
operator will have to work very hard to coerce the press to match the proof,
more than it would have had to, otherwise, if it would have had to match an
AbsCol proof. Now, it's entirely possible that the press will still be able
to match those distorted colors to the client satisfaction -- may not match
perfectly or absolutely. But the mission of the press is very different.
Hope this does not sound too convoluted.
> unless the substrates have the same white point,
Ah! Let's pretend we're in the situation where the press paper MWP is 89, 0,
4 whereas the proof paper MWP is 94, 0, -4. We can expect some nice
distorsion of tones introduced by the FWA built into the proofing media that
will partly be responsible for some hue shift (that's arguably an entirely
different discussion). But, let's say the proof MWP has not FWA then, as I
experimented with this today, there is a color shift away from the press
"real" colors introduced by the RelCol rendering, resulting in a different
aimpoint for the press operators to hit. They will try their best and may
settle for an appearance match. But in all case, in my humble experience,
they will always try to match the proof absolutely not matter how it is
served to them, rel or abs.
> so such an expectation will only be met by a situation that makes RelCol
> and AbsCol rendering indistinguishable (funny about that!).
That would be impossible, to have the press simultaneously hit relative and
absolute appearance, I understand.
> Why would they be more saturated ?
Maybe the term was a little extreme. Maybe I should have qualified with
'depending of where the color falls in the color space'. If we come back to
my above example where the press paper is rather grayish and yellowish, and
the proofing paper is rather bright and bluish, I think you can see what
will happen to saturated colors like a green or a red apple, or a yellow
banana the minute they hit that proof paper relatively as opposed to
absolutely. If those vivid fruit colors are infused with the hue and
Lightness of the typical No5 SWOP groundwood coated stock, chances are that
some level of saturation will be lost. This "relative" (no pun intended)
desaturation may not happen the same for all tones, I recognize that,
probably not as extreme as the tones progressively get closer to the gray
axis.
> They could be, but this depend on the
> white point shift between the press and the proof.
Yes, my point exactly.
> For instance, if the
> proof white point is whiter (more reflective) than the press white point,
> all the RelCol colors will be shifted slightly in the +X,+Y, +Z direction,
> and become slightly more saturated on the proof.
I'll take 'slightly' ;-)
> Conversely, if the proof
> has a slightly less reflective white point than the press, then the colors
> will be shifted slightly in the -X,-Y,-Z direction, and will be less
> saturated.
True too.
> Graeme Gill.
Roger Breton | Laval, Canada | email@hidden
http://pages.infinit.net/graxx
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