How many color patches are needed for a (good) profile ?

[Ink stained Fingers]

I made another test to compare profiles with based on different patch sheet counts and the impact onto actual prints.

I did this -

- I created several icc-profiles with 96 - 283 -720 - 1440 - 2880 color patches onto the same paper type, a glossy cast coated 210 gr paper by the Action thrift shop.

- I used these profiles and printed a patch sheet with 450 patches - the same patch sheet with the same printer setting - rel col rendering intent and no Black Point Compensation with the different profiles. . I used a patch sheet and not a regular image to compare because I let 1Profiler do the print comparisons and do the statistical values.

- I scanned these 5 sheets and let i1Profiler do the comparison of the scanned patch sheet data - aways against that profile created with 2880 patches.

The software compares all thes 450 patches and calculates the average DeltaE for for all of them

DeltaE = 0.60 for the comparison of a profile created with 2880 vs. 1440 patches


The program displays as well the max peak value of an individual patch, in this case 2.69 .

DeltaE = 0.91 for a profile from 720 vs. 2880 patches

DeltaE = 1.0 for a profile from 283 vs. 2880 patches

DeltaE = 1.4 for a profile from 96 vs. 2880 patches

96 patches fit easily on a 4 x 6 inch paper sheet, 96 patches appear to be enough in comparison to 2880 patches to create a profile with such small deviations.

This 450 patchcount sheet is printed via a profile which does quite some changes to the actual color values - based on the rendering intent how out of gamut colors are reassigned to color values inside the printer gamut or on the edge of it.

This becomes visible with the Gamutvision program

The screen copy displays both the sRGB gamut and the printer gamut inside of it. Attention is drawn to the lower part of the display - showing some small light arrows pointing from the surface of the sRGB gamut to some points on the boundary of the printer gamut. All colors outside the printer gamut are remapped to colors on the printer gamut as the vectors show, and these vectors have a different direction if you choose another rendering intent. It is apparent that the color saturation and hue changes are significant, these changes are much wider than the small changes between the number of color patches used for the profile generations in this test.
It is my conclusion that I'm already getting quite a good profile just with 96 color patches which does not differ much from a profile created with 2880 patches.

 

[pharmacist]

I think the Colormunki/i1Studio/Calibrite method using the 50 + 50 patch method is actually based on these findings. The difference is the measurement of the first patch set of 50 gives a good idea how the curvature of the RGB-model will be and calculates the estimated end colour, what should be and reads this end colour again and corrects it again what the exact curvature should be and thus estimating the final profile.

The original MacBeth iMatch software 20 years ago has a simple target that only uses 45 patches..... So I understand the Spyderprint 225 patch high quality target is for most of the users more than enough to get a more than satisfactory profile. I was able to squeeze this 225 patch target on a single 10x15 cm photo card and indeed: not difference visually compared to a higher 700 patch target.