Re: Rel vs Abs proofs
Re: Rel vs Abs proofs
- Subject: Re: Rel vs Abs proofs
- From: Graeme Gill <email@hidden>
- Date: Thu, 12 Oct 2006 12:46:36 +1000
Roger Breton wrote:
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.
They are likely to be disappointed then, are they not, if they expect
an exact match ?
> 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.
It's quite normal to strive for a match to a proof, but if it is not
a proof that has been created deliberately to be within the range of
adjustment for a particular device, then there should be no expectation
that an exact match will be achievable.
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.
It will be up to the experience, practice and discretion of the press
operator as to what aspects they trade-off, and what the end result
therefore looks like. With a particular results, you are often
never quite sure if some other setting would give a better result,
or whether it would just result in a different set of compromises,
that may appeal to some observers more than others.
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.
Roger, if the white points match, there is no difference between AbsCol
and RelCol rendering, they are exactly the same.
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.
There are two possible effects at work in how the RelCol and AbsCol
will differ. One is the effect of the mathematics on the XYZ of the
white point. As I mentioned, if the XYZ gets scaled up slightly
because the proof white point is whiter than the press, then
this has the effect of increasing saturation. There will of
course be other analogous visual effects if the hue or saturation of
the white points differ as well. The other effect is that of
whether the gamut of the proof comes into, or goes out of play
because of the shift of the press gamut to proof gamut mapping.
Graeme Gill.
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