Digital BW, The Print

Steve,

First I need to apologize : I have double posted the below in here and 
QTR group which is not very ethical... In fact I just realised as you 
below mentionned that Roy would be of help in this.

I did look at the kTRC explanation and also the color.org explanation 
of BPC, apparently this is an issue the organisation is wanting to 
tackle, I don't know if this is being implemented in v4 or not, but by 
experince not all soft (profilers, don't know about editing 
softs) "understand" v4. There's also a lack of standardised perceptual 
intents (seems all profilers implement a proprietary algorithm) which 
is also something they are looking at, and to make it even more 
confusing there's now a debate about CIE Lab as a PCS (it does not see 
the same for XYZ)due to hue shifting thus non-uniformity... Also this 
is simply and unfortunately coming from booking reading and web 
browsing : I try to know but seldomly understand.   

Anyway, in fact what happens is that since my PS color settings is 
(default, I never bothered to set it properly)grey : dot 15% I work 
with too "light" a working space and since the stepwedge is not tagged 
PS assumes the dot 15% as a source space thus printing light after 
converting.

I'd like to measure the actual output of the QTR-ICC profiling but I 
feel it's a lost search. When printing the raw stepwedge in QTR, datas 
are fed irrespective of color space, so the raw L* value are dependent 
on printer-ink-paper and does not reflect...anything else than the 
linearised stepwedge printed on ONE printer with ONE ink set and ONE 
paper.  May be there's a way to translate the linear L* measurements 
into a gamma and set it as a grey working space to perform the 
conversion with the QTR ICC profile to evaluate, but I don't know it. I 
asked Roy if 1.8 would make sense. If not I leave it here since anyway 
it will not improve the workflow. I'll set color settings grey : gamma 
2.2 (RVB and the windows environment) to minimize conversions and that 
will do.

BPC remains a mystery : I use to do the soft-proofing with 
perceptual+BPC+white paper (which also turns on Blakc ink). However it 
might be that you need/can soft proof not turning BPC but Black ink 
simulation (which is done when white paper is checked)... to be 
followed since it's only my understanding.

I'm sure I'm tiring many people with some lack of competence/knowledge 
and not-so-important issues... So, thanks Steve for your great 
willingness to help, I do appreciate a lot.

Olivier


--- In DigitalBlackandWhiteThePrint@yahoogroups.com, Steve Kale 
<stevekale@b...> wrote:
> Olivier
> 
> Roy should step in here but (1) the ICC spec discusses how the kTRC 
data
> should be scaled for media white point-relative colorimetry and (2) 
in the
> documents section of www.color.org you will also find a discussion 
paper on
> Adobe black point compensation.  Roy has done both the black and 
white point
> scaling.
> 
>