Digital BW, The Print

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, Steve Kale <stevekale@=
b...> 
wrote:
> A couple more basic questions and sorry if this is fundamental ³colour
> theory².  What about the K in your CMYK readings? I still struggle to thi=
nk
> in RGB, let alone CMYK.  R=G=B=x gives me a dead neutral shade of grey,
> correct?  What would be warm/cool in RGB terms?
> 
> Roy and Carl:  I was wondering if it made sense to incorporate some of th=
e
> math posted by Carl into, say,  Run-Calc-Density so that you can get a se=
nse
> of measured rather than eyeballed warmth/coolness/neutrality of a curve o=
r
> curve combination.  Perhaps the calculations are too difficult ­ it is
> certainly way beyond my understanding for now.
> 
> Getting there slowly...
> 
> Steve
> 

The data files from MeasureTool have all the Lab data and some other info.
I wrote Calc-Density mainly to get the linearize data, but it is very helpf=
ul
to look at the full Lab info.   I just about always read the MT file into a=

AppleWorks spreadsheet and graph the L, a, and b data -- takes about 30
seconds or less.   Lab is actually very convenient, L should be a straight
line, a and b should smoothly go from paper white to ink black.

> 
> But what I just found interesting was to look at the 21 step wedge file i=
n
> PS with mode set to RGB (Adobe RGB 1998) and observing in the Info Palett=
e
> the relative RGB values and CMYK values.  For each step, R=G=B but in eac=
h
> case C>Y (and M=Y or only 1% more).....at the 100% patch C=75, M=68, Y=67=
,
> K=90.
> 
> ???
> 
> Steve
> 

I have limited color expertise but just about all CMYK setups have more cya=
n
in the mix for a neutral gray.  CMYK values in general are amounts of ink
on the paper, but what Paul is measuring is reflective densities.  Certainl=
y
related but different numbers.

Roy