Digital BW, The Print

This is exactly the chart I was going to make for myself. Thanks for 
saving me the trouble, Roy.

For comparison, I plotted Roy's ideal density measures along with my 
actual measures from output using the PiezoBW ICC profiles and Warm 
Neutral w/Museum Black ink. I printed a 21-step wedge on Epson 
Enhanced Matte, Epson Velvet Fine Art, Hahnemuhle Photo Rag, and 
Museum Bright White-148 paper (all measures taken after 24-48 hours 
of dry down). Several of the papers had different dMin values but I 
was mostly interested in seeing the approximate relationship between 
the curves.

Interestingly, the PiezoBW ICC profiles appear to have a very gentle 
S curve in relation to the Lab curve. For the most part, the values 
of K between 0 and 55% print below the Lab curve, cross over around 
60% and remain above the Lab curve through to 100%. Also of note, on 
each paper the 95% and 100% values measure approximately the same, 
which can be seen in slightly blocked-up shadows in my prints.

Here's a comparison of Roy's ideal densities (adjusted for a paper 
base of .05) and Hahnemuhle Photo Rag (HPR):

        Lab     HPR
0	0.05	0.05
5	0.10	0.10
10	0.15	0.14
15	0.20	0.19
20	0.25	0.23
25	0.30	0.29
30	0.36	0.34
35	0.42	0.39
40	0.48	0.45
45	0.55	0.50
50	0.62	0.52
55	0.69	0.58
60	0.77	0.70
65	0.85	0.86
70	0.94	1.02
75	1.04	1.21
80	1.14	1.34
85	1.25	1.45
90	1.37	1.57
95	1.50	1.66
100	1.65	1.63

Since the results from each of the PiezoBW ICC profiles was 
approximately the same I have to believe they did it on purpose ;~) 
I wonder if this is to account for specific perceptual issues that 
the Lab model doesn't account for?

Any thoughts?

Thanks,
Peter.


--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Roy 
Harrington" <roy@h...> wrote:
> 
> I don't know if this is really what you want, but I have a table of
> my "ideal" densities for the 21 steps given a dMax.   It's in my
> QTR download under CurveDesign, the file is called 
ideal_density.pdf
> 
> If you'd like, email me and I'll email the pdf to you.
> 
> Roy
>