[argyllcms] Photocamera calibration questions
- From: yan@xxxxxxxxxxxxxxxxx
- To: <argyllcms@xxxxxxxxxxxxx>
- Date: Tue, 17 May 2011 10:51:35 +0400
Hello!
I use argyll for photo camera calibration. I found
spectral responce curvers for Canon EOS 5d and 5d mark II. (here -
http://astrosurf.com/buil/50d/test.htm ) So, now I simulate XYZ and
camera responce for some number of paint's of known spectral responce
under some light with known visible spectral curve.
I use 19 colors:
18 color patches from colochecker24 and 1 "pure white". Spectral
responce for colorcheker and standart 4500K light coluld be found in
internet easilly. So, it gives 19.
I need to get a "gamma 2.2". I
suppose camera sensor is linear, and "dcraw -o 0 -g 2.2 0" gives pure
"gamma 2.2" raw file. So, I have to make 255*19 charts, for every
brightness, and a "0 0 0" for black. It gives 4846 color charts. So,
first question:
1. IS IT POSSIBLE TO SET "GAMMA 2.2" IN INPUT FOR
COLPROF UTILITY SOMEHOW, NOT BY MAKING A LOT OF "AUXILIARY COLOR
CHARTS"?
Next,
I use this script:
@echo off
set manufacture=-A
"Canon"
set model=-M "EOS 5D mark II"
set desc=-D "EOS 5D mkII, 4500K,
matrix"
set common=-qu -v set mode=-aG
set input=4500
set output=-O
Canon_5Dmk2_4500K_matrix.icm
colprof -v %manufacture% %model% %desc%
%mode% %output% %input%
(with this 4500.ti3 file
http://lj.vladimirovich.net/lj11/spectral/4500.zip, so you could
download, unzip and try yourself).
And it gives me result:
No of
test patches = 4846
Creating matrix and curves... 100%
Matrix = 0.832540
-0.023902 0.143377
0.348156 0.766601 -0.124534
0.026696 -0.169944
0.969710
Gamma = 2.196714
Find white & black points
White point XYZ =
0.039651 0.041242 0.034422
Black point XYZ = 0.000000 0.000000
0.000000
Fixup matrix for white point
After white point adjust:
Matrix =
20.266359 -0.537054 3.421069
8.477817 18.560198 -3.028086
0.636536
-4.059754 23.229008
Done gamma/shaper and matrix creation
Profile
done
Profile check complete, peak err = 4.545609, avg err = 1.047500
So, next question:
2. WHY WHITE POINT IS "0.039651 0.041242
0.034422" AND NOT
A19 96.42 100 82.491 100 100 100 1.00000000 1.00000000
1.00000000
FROM A TI3 FILE?
Thank you,
Yan Sizov
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