[argyllcms] Measuring a colorcheker on screen
- From: "Lars Tore Gustavsen" <lars.tore@xxxxxxxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Tue, 22 Jan 2008 23:27:27 +0100
I found an old Seybold Report with the title "Measuring the quality of
ICC profiles"
http://www.heidelberg.com/wwwbinaries/bin/files/dotcom/en/prinect/prinect_profile_toolbox.pdf
. On monitor profiles they have three objective test for the quality.
The are, page 13, archived gamma, DE difference in whitepoint from
target D50 and the last one average DE for a colorcheker measured on
monitor.
I tried to do the last step. I found a digital LAB version of the
colorchecker
http://www.colorremedies.com/realworldcolor/downloads/Macbeth_ColorChecker_LAB.tif.zip
I fixed? (added a white patch nr 25) to the colorcheker.ti2 in the ref
directory(attached), and measured the colorchecker when I viewed it
with cinepaint with colormanagment on. I then measured it with
"chartread -d -H ColorChecker" with my eye-one pro.
When I afterwards did a "profile -v -as Colorcheker" I get an avg DE
on 5.6. I get some real big mismatch on a few of the patches (set
profcheck output) There is DE of 60 on patch 16. I guess this yellow
patch is out of gamut. I find it hard to understand why they have
included out of gamut measurements.
I also get a quit big error on patch 20( its L*81) with a DE of about
18. I don't understand why since I get pretty nice numbers when I did
the calibration with dispcal. I have attached a log for my
calibration/profiling today.
Do you think this is something similar to what they have done in the
Seybold Report? I don't expect that I should match those numbers since
I have a pretty old monitor, but it's always fun to experiment a
little and maybe learn something.
Lars Tore Gustavsen
DE Patch
0.434580 8
0.560124 22
0.608833 21
0.618981 24
1.070394 13
1.160494 4
1.267156 2
1.344788 5
1.578218 11
1.871612 3
1.872423 18
2.014564 1
2.065875 23
2.212793 10
2.648374 14
2.901850 9
3.749590 25
4.027044 17
4.681445 15
5.525888 6
6.098186 19
6.916798 12
7.878428 7
17.966567 20
59.859779 16
Matrix = 0.428105 0.289633 0.134801
0.232963 0.657081 0.065105
0.012379 0.081610 0.600622
Offset = -0.019995 0.006099 -0.078470
0 harmonics = 2.022386 2.215874 3.186807
1 harmonics = 0.284609 0.031071 -0.799580
2 harmonics = -0.241875 0.158033 -2.099517
3 harmonics = 0.161734 -0.497972 1.131950
4 harmonics = -0.102582 0.273724 -0.173979
5 harmonics = -0.019623 0.091990 -0.847132
6 harmonics = -0.019853 -0.381095 -0.224354
7 harmonics = 0.010040 0.032083 0.291994
8 harmonics = -0.065277 0.264820 0.190591
9 harmonics = 0.015681 -0.120464 -0.642684
Find white & black points
White point = 0.852539 0.955149 0.694612
Black point = 0.001767 0.004008 0.000498
White point XYZ = 0.852539 0.955149 0.694612
Black point XYZ = 0.001767 0.004008 0.000498
Fixup matrix for white point
After white point adjust:
Matrix = 0.472461 0.333220 0.158519
0.252240 0.674857 0.072903
0.014574 0.090830 0.719496
Done gama/shaper and matrix creation
Profile done
profile check complete, peak err = 59.859779, avg err = 5.637391
Matrix = 0.444118 0.322434 0.122681
0.249509 0.646798 0.089312
0.004784 0.105506 0.629647
Offset = 0.004658 0.004922 0.004948
0 harmonics = 2.235037 2.187631 2.240639
1 harmonics = -0.060557 0.009011 -0.051760
2 harmonics = -0.070965 -0.068296 -0.064065
3 harmonics = -0.029771 -0.017513 -0.028094
4 harmonics = -0.005864 -0.044992 -0.044253
5 harmonics = 0.005867 -0.007206 0.010208
6 harmonics = -0.029305 -0.017600 -0.047362
7 harmonics = -0.022299 -0.032295 -0.030591
8 harmonics = -0.037681 -0.050462 -0.038819
9 harmonics = -0.035846 -0.058410 -0.047354
Find white & black points
White point = 0.889233 0.985619 0.739936
Black point = 0.004263 0.004788 0.003657
White point XYZ = 0.889233 0.985619 0.739936
Black point XYZ = 0.004263 0.004788 0.003657
Fixup matrix for white point
After white point adjust:
Matrix = 0.472454 0.354112 0.137633
0.260412 0.646707 0.092882
0.005048 0.113460 0.706392
Done gama/shaper and matrix creation
Profile done
profile check complete, peak err = 4.776828, avg err = 1.030138
Setting up the instrument
Instrument Type: Eye-One Pro
Serial Number: 306673
Firmware version: 502
CPLD version: 999
Date manufactured: 16-2-2007
U.V. filter ?: No
Measure Ambient ?: Yes
Tot. Measurement Count: 1386
Remission Spot Count: 84
Remission Scan Count: 171
Date of last Remission spot cal: Mon Jan 21 18:39:15 2008
Remission Spot Count at last cal: 79
Total lamp usage: 727.580078
Place the instrument on its reflective white reference Serial no. 306673,
and then hit any key to continue,
or hit Esc, ^C or Q to abort:
Calibration complete
Place instrument on test window.
Hit Esc, ^C or Q to give up, any other key to continue:
Target white = native white point
Target brightness = native brightness
Target gamma = 2.200000
Commencing device calibration
patch 6 of 6
Black = XYZ 0.31 0.28 0.28
Red = XYZ 50.29 27.87 0.64
Green = XYZ 37.68 74.68 11.15
Blue = XYZ 13.49 10.89 69.95
White = XYZ 101.50 113.53 81.91
patch 80 of 80
Initial native brightness target = 113.528561 cd/m^2
Target white value is XYZ 101.502137 113.528561 81.913943
Adjusted target black XYZ 0.24 0.27 0.20, Lab 2.16 0.00 0.00
Target black after min adjust: XYZ 0.34 0.38 0.27, Lab 3.03 -0.00 0.00
Current gamma curve offset = 0.111086, Gamma curve power = 2.594250
Total Iteration 4, Final Samples = 96 Final Repeat threshold = 0.500000
Creating initial calibration curves...
Doing iteration 1 with 12 sample points and repeat threshold of 4.000000 DE
patch 12 of 12
Brightness error = 0.000000 cd/m^2
White point error = 0.000000 deltaE
Maximum neutral error (@ 0.875085) = 3.769726 deltaE
Average neutral error = 2.431266 deltaE
Computing update to calibration curves...
Doing iteration 2 with 24 sample points and repeat threshold of 2.000000 DE
patch 24 of 24
Brightness error = 0.000000 cd/m^2
White point error = 0.000000 deltaE
Maximum neutral error (@ 0.227985) = 1.995954 deltaE
Average neutral error = 1.037829 deltaE
Computing update to calibration curves...
Doing iteration 3 with 48 sample points and repeat threshold of 1.000000 DE
patch 48 of 48
Brightness error = 0.000000 cd/m^2
White point error = 0.000000 deltaE
Maximum neutral error (@ 0.000000) = 1.523348 deltaE
Average neutral error = 0.580272 deltaE
Computing update to calibration curves...
Doing iteration 4 with 96 sample points and repeat threshold of 0.500000 DE
patch 96 of 96
Brightness error = 0.000000 cd/m^2
White point error = 0.000000 deltaE
Maximum neutral error (@ 0.000000) = 1.365594 deltaE
Average neutral error = 0.359014 deltaE
The instrument can be removed from the screen.
Written calibration file 'TargetA.cal'
Calibration complete
Place instrument on test window.
Hit Esc, ^C or Q to give up, any other key to continue:
Current calibration response:
Black level = 0.37 cd/m^2
White level = 111.13 cd/m^2
Aprox. gamma = 2.13
Contrast ratio = 299:1
White chromaticity coordinates 0.3426, 0.3792
White Correlated Color Temperature = 5164K, DE to locus = 15.3
White Correlated Daylight Temperature = 5171K, DE to locus = 13.0
White Visual Color Temperature = 4764K, DE to locus = 14.9
White Visual Daylight Temperature = 4866K, DE to locus = 12.6
The instrument can be removed from the screen.
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