[argyllcms] Re: relativ volume of gamut -- vrml comparison?

I was inspired by Klaus and made some tests with the modified tiffgamut.
My idea with these test was to show, if there is any idea in using
wide gamut profiles like ProphotoRGB, when data comes from the camera.
In a second run of the tests, I changed the flags for timage to give
16 bit precision and smooth flag, but it gave only small changes (i.e
< 1%).

The profile 6071_F.icc used below is Canon's profile for the 350D
camera, faithful colors.
When the data was coming from the camera profile, AdobeRGB showed a
larger gamut, than when I calculated the gamut directly from the
camera profile. I am aware, that input devices do not have gamuts, but
I don't understand how this happens.
So next I tried to use the precision flag -p in cctiff, and this gave
huge changes in the calculated gamut volumes, but only when the camera
profile was involved.

Can AdobeRGB expand the camera's gamut?
Can somebody explain what happens?

timage -t -x -s timage_txs.tif

Gamut for the camera profile:
tiffgamut -v 6071_F.icc timage_txs.tif
Total volume of gamut is 1062744.608376 cubic colorspace units

Gamut for AdobeRGB:
tiffgamut -v adobergb1998.icc timage_txs.tif
Total volume of gamut is 1309781.877088 cubic colorspace units

Gamut for camera to AdobeRGB:
cctiff -ir 6071_F.icc -ir adobeRGB1998.icc timage_txs.tif timage_txs_comb.tif
tiffgamut -v adobergb1998.icc timage_txs_comb.tif
Total volume of gamut is 1143481.853788 cubic colorspace units

Gamut for camera to AdobeRGB, with -p flag:
cctiff -p -ir 6071_F.icc -ir adobeRGB1998.icc timage_txs.tif timage_txs_comb.tif
tiffgamut -v adobergb1998.icc timage_txs_comb.tif
Total volume of gamut is 1285131.198467 cubic colorspace units

Result for the combination camera profile / ProphotoRGB (Again without
and with -p flag):

tiffgamut -v prophoto.icm timage_txs.tif
Total volume of gamut is 2899242.733546 cubic colorspace units

cctiff -ir 6071_F.icc -ir prophoto.icm timage_txs.tif timage_txs_comb.tif
tiffgamut -v prophoto.icm timage_txs_comb.tif
Total volume of gamut is 1062789.167314 cubic colorspace units

cctiff -p -ir 6071_F.icc -ir prophoto.icm timage_txs.tif timage_txs_comb.tif
tiffgamut -v prophoto.icm timage_txs_comb.tif
Total volume of gamut is 1670486.450441 cubic colorspace units

Results for wideGamutRGB are similar to the results for ProphotoRGB.

Preben Soeberg

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