ColorMunki: Merit in Using Higher Patch-count?

[feppe]

Once more again about the accuracy of printer profiles.
I have evaluated the accuracy of profiles using (printing and measuring) the "adapted" Ugra/Fogra Media Wedge CMYK v3.0 testchart.
Printer: Canon PIXMA Pro9500
Paper: Epson Archival Matte Paper
1. The ColorMunki printer profile, standard profiling (50+50 patches)
   avr dE00=1.6, max dE00=3.3
2. The ColorMunki printer profile, profiling with additional patches (450 patches in total)
   avr dE00=1.52, max dE00=3.11
3. The printer profile created with i1Pro UV-cut and ProfileMaker 5.0.8 from 283 unique patches
   avr dE00=1.81, max dE00=3.87
4. The printer profile created with i1Pro UV-cut and ProfileMaker 5.0.8, TC9.18 (918 unique patches)
   avr dE00=1.08, max dE00=2.85
5. The printer profile created with i1Pro UV-cut and ProfileMaker 5.0.8 from 2244 unique patches
   avr dE00=0.98, max dE00=2.81

Interpreting this with my very limited knowledge of delta-E values, doesn't it mean that the difference between the profiles produced with 100 and 2,244 patches is imperceptible to the human eye, thus only useful for academic purposes (and I presume some highly specialized technical work)?

[digitaldog]

First of all I do not know any common used method to evaluate the accuracy of an "RGB-"printer, http://luminous-landscape.com/forum/index....showtopic=41048

I don’t know there are any. The matrixes uses to provide a numeric scale is somewhat flawed. See http://luminous-landscape.com/forum/index....36&hl=istar

It doesn’t answer your question about a common method but does define a far better approach to providing a useful matrix scale (note also the number of deltaE formula adjustments over the years!).

[probep]

doesn't it mean that the difference between the profiles produced with 100 and 2,244 patches is imperceptible to the human eye, thus only useful for academic purposes?

The color difference between the profiles produced with 100 and 2,244 patches is perceptible: avr dE00=1.07, max dE00=2.48

[neil snape]

Interesting thread, didn't have time to read it all.

I do have once again point out accuracy vs precision.

X-Rite are not going to go into that arena for the CM, nor it's software. What it is doing exactly is not something they would want to let you know.

Yet based on experience, I'd say the second or more iterations on the CM profile are to align grid points to new measured samples to reduce S/N, and sample mean deviation.

Accuracy is a  result of the precision of the profile adjusted with more or different grid points, their weighting, etc.

So I could be wrong but I think the iterative profiling adds precision not necessarily accuracy.

[neil snape]

The color difference between the profiles produced with 100 and 2,244 patches is perceptible: avr dE00=1.07, max dE00=2.48

If so >dE 1 average and maximum are both for good eyes perceptible.

That is of course comparing a very limited sample of colours from what I see in the jpg of a chart >