CAM Color Appearance Model , most recent model is CIECAM02 as of 2008
CGATS Graphic Arts Technologies Standards
cLUT Color Look Up Table
CIE CIE is the short for Commission Internationale de l'Eclairage which is the french title of the
international commission on light
CMM Color Matching Module
CMS Color Management System
ICC International Color Consortium
Lab Lab is now more often used as an informal abbreviation for CIELAB or CIE 1976 ,
whose coordinates are actually L*, a*, and b*.
RelCol Relative Colorimetric
MinCD Minimum Color Difference
OOG Out Of Gamut
PCS Profile Connection Space
TRC Tone Response Curve
WCS Windows Color Management
Tuesday, 22 March 2011
Saturday, 19 March 2011
Evaluation of RGB calibration with CT3
Argyllcms 1.3.2
ColorThink Pro 3 [ link ]
Scanner target: Kodak IT8 Q60 reflective
Epson V500 scanner
Comparison:
a) colprof -v -qh -ax scanner
b) colprof -v -qh -ax -u scanner
c) colprof -v -qh -ax -un scanner
d) MP - profile created with Monaco Profiler 4.8
Note:
The L-axis represents the ideal neutral gray or R=G=B. The goal of most gamut mapping algorithms is to map source neutrals to device neutrals. A better calibrated profile would have neutral points stay closer to the neutral axis.
ColorThink Pro 3 [ link ]
Scanner target: Kodak IT8 Q60 reflective
Epson V500 scanner
Comparison:
a) colprof -v -qh -ax scanner
b) colprof -v -qh -ax -u scanner
c) colprof -v -qh -ax -un scanner
d) MP - profile created with Monaco Profiler 4.8
 |
| Evaluate device RGB neutrals |
 |
| Enlarged view: near White |
 |
| Enlarged view: near Black |
 |
| with option -al, from different perspective |
Note:
The L-axis represents the ideal neutral gray or R=G=B. The goal of most gamut mapping algorithms is to map source neutrals to device neutrals. A better calibrated profile would have neutral points stay closer to the neutral axis.
Argyll scanner profiles' AtoB & BtoA tags
Argyllcms 1.3.2
Scanner target: Kodak IT8 Q60 reflective
Commands:
a) colprof -v -qh -al scanner
b) colprof -v -qh -al -u scanner (Forces cLUT profile absolute)
c) colprof -v -qh -al -un scanner (Forces cLUT profile absolute but cLUT white &
black points will not be extrapolated with matrix)
Option -u
The -u option causes the lut based input profile to be generated in such a way that the lut table defaults to absolute color values, in that the white of the reference chart will be mapped to its absolute value. Any value whiter than the white reference will not be clipped by the profile, wheares values outside the range of the reference chart will be extrapolated.
AtoB tag
BtoA tag
Scanner target: Kodak IT8 Q60 reflective
Commands:
a) colprof -v -qh -al scanner
b) colprof -v -qh -al -u scanner (Forces cLUT profile absolute)
c) colprof -v -qh -al -un scanner (Forces cLUT profile absolute but cLUT white &
black points will not be extrapolated with matrix)
Option -u
The -u option causes the lut based input profile to be generated in such a way that the lut table defaults to absolute color values, in that the white of the reference chart will be mapped to its absolute value. Any value whiter than the white reference will not be clipped by the profile, wheares values outside the range of the reference chart will be extrapolated.
AtoB tag
BtoA tag
Friday, 18 March 2011
Perfect White Point for scanner profile
Perfect White Point for non-Absolte Colorimetric Intents
Monaco profiler 4.8
XYZ: 0.9641876, 1., 0.8248901
Lab: 100.00, -0.018456, 0.017265
PhotoGamutRGB_avg6c.icc < Link >
XYZ: 0.9641724, 1., 0.8248749
Lab: 100.00, -0.0210935, 0.0184981
a) ArgyIIcms 1.3.2
b) Basiccolor display 4.1.22
c) Epson (perv50_r.icm, perv50_r.icm)
XYZ: 0.9642029, 1., 0.8249054
Lab: 100.00, -0.0158185, 0.016032
Monaco profiler 4.8
XYZ: 0.9641876, 1., 0.8248901
Lab: 100.00, -0.018456, 0.017265
PhotoGamutRGB_avg6c.icc < Link >
XYZ: 0.9641724, 1., 0.8248749
Lab: 100.00, -0.0210935, 0.0184981
a) ArgyIIcms 1.3.2
b) Basiccolor display 4.1.22
c) Epson (perv50_r.icm, perv50_r.icm)
XYZ: 0.9642029, 1., 0.8249054
Lab: 100.00, -0.0158185, 0.016032
Converting from ProPhoto in Photoshop
ProPhoto's negative primaries [ Link ]
ProPhoto uses PCS of XYZ and its primaries have a* and b* values exceeding the range -128 to 127. When converting color in Photoshop, color out of this Lab gamut space would be cripped to the defined limits.
White Point for ProPhoto
Red: 0.797668, 0.288040, 0.000000
[Lab 60.608273, 139.168888, 104.497022]
Green: 0.135193, 0.711884, 0.000000
[Lab 87.576439, -186.694184, 150.993860]
Blue: 0.031342, 0.000092, 0.824905
[Lab 0.082699, 90.249204, -172.271644]
Lack of appropriate Gamut Mapping
Example:
XYZ ( 16.010934 0.663729 138.946202 )
= Lab ( 5.995 180.014 -200.008 )
--> Lab ( 5.995 127 -128) = aRGB ( 6.425 -67.615 207.751 )
--> aRGB ( 6.425 0 207.751 )
see [ link ]
White Point for ProPhoto
Red: 0.797668, 0.288040, 0.000000
[Lab 60.608273, 139.168888, 104.497022]
Green: 0.135193, 0.711884, 0.000000
[Lab 87.576439, -186.694184, 150.993860]
Blue: 0.031342, 0.000092, 0.824905
[Lab 0.082699, 90.249204, -172.271644]
 |
| ProPhoto colorants |
Example:
XYZ ( 16.010934 0.663729 138.946202 )
= Lab ( 5.995 180.014 -200.008 )
--> Lab ( 5.995 127 -128) = aRGB ( 6.425 -67.615 207.751 )
--> aRGB ( 6.425 0 207.751 )
see [ link ]
Thursday, 17 March 2011
dtp41.cht
BOXES 13
F _ _ 132 520 282 520 285 2144 129 2144
D ALL ALL _ _ 158 1627 126 516 0 0
D MARK MARK _ _ 14 14 129 516 0 0
Y 01 01 A K 125 90 148 540 0 148.7
BOX_SHRINK 3.5
REF_ROTATION -0.443070
XLIST 13
48.773780 0.051474 0.428571
.....
YLIST 68
26.796151 0.033614 0.142857
......
EXPECTED XYZ 11
A01 0 0 0
B01 4.89 3.27 1.6
C01 5.87 3.31 1.33
D01 6.3 3.38 1.19
E01 13.01 11.44 7.64
F01 16.14 11.99 6.81
G01 19.35 12.41 6.06
H01 20.41 11.97 5.3
I01 43.5 42.81 32.65
J01 45.58 42.37 30.95
K01 48.99 43.2 29.9
BOXES 13
F _ _ 28 510 390 510 390 2144 28 2144
D ALL ALL _ _ 158 1627 126 516 0 0
D MARK MARK _ _ 14 14 129 516 0 0
X A A 01 11 125 90 148 540 5 148.7
BOX_SHRINK 3.5
REF_ROTATION -0.443070
XLIST 13
48.773780 0.051474 0.428571
.....
YLIST 68
26.796151 0.033614 0.142857
.....
EXPECTED XYZ 11
A01 0 0 0
A02 4.89 3.27 1.6
A03 5.87 3.31 1.33
A04 6.3 3.38 1.19
A05 13.01 11.44 7.64
A06 16.14 11.99 6.81
A07 19.35 12.41 6.06
A08 20.41 11.97 5.3
A09 43.5 42.81 32.65
A10 45.58 42.37 30.95
A11 48.99 43.2 29.9
Notes:
a) Number of Boxes = Expected number of patches + 2
b) The generated number of labels = Expected number of patches
Considerations in creation of Input profiles
Choice of PCS (Profile Connection Space)
For practical consideration, ICC has imposed L*a*b* encoding range of -128 to +127 for values a* and b* [link]. In reality, those out of range colors are not imaginary but visible and they can be encoded in a PCS of XYZ icc profile.
[ Negative primaries ]
ProPhoto primaries have either a* or b* that exceed the -128 to 127 range, as shown below.
Red: 0.797668, 0.288040, 0.000000 [Lab 60.608273, 139.168888, 104.497022]
Green: 0.135193, 0.711884, 0.000000 [Lab 87.576439, -186.694184, 150.993860]
Blue: 0.031342, 0.000092, 0.824905 [Lab 0.082699, 90.249204, -172.271644]
[ colprof ]
colprof with options -a, -u and -un
-a lxXgsmGS Algorithm type override
l = Lab cLUT (def.), x = XYZ cLUT, X = display XYZ cLUT + matrix
g = gamma+matrix, s = shaper+matrix, m = matrix only,
G = single gamma+matrix, S = single shaper+matrix
Option -al
Default option, cLUT profile will be created with PCS of L*a*b*. Profiles that are generated with this option support all the four rendering intents.
Option -ax
This option allows cLUT profile to be created with PCS of XYZ which offers better accuracy for input devices such as displays, scanners and cameras. In general, it avoids clipping of values above the white point that can occur in L*a*b* based cLUT input profile.
Option -u
Forces cLUT profile absolute.
Option -un
Forces cLUT profile absolute but cLUT white & black points will not be extrapolated with matrix.
Profile Gamut Volume (absolute intent) recorded with CT3
-qh -al 2,336,270
-qh -al -u 3,148,510
-qh -al -un 2,538,190
-qh -ax 2.230,620
-qh -ax -u 2,443,380
-qh -ax -un 2,360,950
For practical consideration, ICC has imposed L*a*b* encoding range of -128 to +127 for values a* and b* [link]. In reality, those out of range colors are not imaginary but visible and they can be encoded in a PCS of XYZ icc profile.
[ Negative primaries ]
ProPhoto primaries have either a* or b* that exceed the -128 to 127 range, as shown below.
Red: 0.797668, 0.288040, 0.000000 [Lab 60.608273, 139.168888, 104.497022]
Green: 0.135193, 0.711884, 0.000000 [Lab 87.576439, -186.694184, 150.993860]
Blue: 0.031342, 0.000092, 0.824905 [Lab 0.082699, 90.249204, -172.271644]
[ colprof ]
colprof with options -a, -u and -un
-a lxXgsmGS Algorithm type override
l = Lab cLUT (def.), x = XYZ cLUT, X = display XYZ cLUT + matrix
g = gamma+matrix, s = shaper+matrix, m = matrix only,
G = single gamma+matrix, S = single shaper+matrix
Option -al
Default option, cLUT profile will be created with PCS of L*a*b*. Profiles that are generated with this option support all the four rendering intents.
Option -ax
This option allows cLUT profile to be created with PCS of XYZ which offers better accuracy for input devices such as displays, scanners and cameras. In general, it avoids clipping of values above the white point that can occur in L*a*b* based cLUT input profile.
Option -u
Forces cLUT profile absolute.
Option -un
Forces cLUT profile absolute but cLUT white & black points will not be extrapolated with matrix.
 |
| cLUT Lab bsed Profiles, illustrated with Lab co-ordinates, relative rendering and showing white point at L=100 (same scale) |
-qh -al 2,336,270
-qh -al -u 3,148,510
-qh -al -un 2,538,190
-qh -ax 2.230,620
-qh -ax -u 2,443,380
-qh -ax -un 2,360,950
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