[argyllcms] Re: Perceptual intent
- From: <robert@xxxxxxxxxxxxxxxxxx>
- To: <argyllcms@xxxxxxxxxxxxx>
- Date: Tue, 16 Dec 2014 21:42:41 -0000
Hi Graeme,
As per my email to you, I am using GamutVision from Imatest to view things
like the 3D Lab gamut and black and white density response curve. (I've
resent the email as I can't show graphics on this mail list. The email also
contains links to the profiles, Argyll .tix files etc).
So my figure for the DMax is computed by GamutVision.
I really don't understand what you are showing me with your Fogra39 example.
Here are results from xicclu for the Argyll and i1Profiler profiles for the
same paper:
H:\bin> xicclu -ff -ip iPF6400-Canson-Baryta-310-Argyll-2584.icc
0 0 0
0.000000 0.000000 0.000000 [RGB] -> Lut -> 3.060566 -0.115180 1.191879 [Lab]
1 1 1
1.000000 1.000000 1.000000 [RGB] -> Lut -> 100.000000 -0.000062 0.000060
[Lab]
H:\bin> xicclu -ff -ip iPF6400-Canson-Baryta-310-i1Profiler-2584.icm
0 0 0
0.000000 0.000000 0.000000 [RGB] -> Lut -> 0.000000 -0.093750 0.097656 [Lab]
1 1 1
1.000000 1.000000 1.000000 [RGB] -> Lut -> 100.000000 0.000000 0.000000
[Lab]
An L* value of 0.0 from i1Profiler does seem a bit suspicious! However the
Argyll L* value of 3.0605 works out at a DMax of 2.47 according to Bruce
Lindbloom's companding calculator, so it seems that GamutVision is getting
things wrong (DMax of 2). This is assuming xicclu is giving the right value
and that I'm using the command correctly.
The relative values are more realistic for i1Profiler:
H:\bin> xicclu -ff -ir iPF6400-Canson-Baryta-310-Argyll-2584.icc
0 0 0
0.000000 0.000000 0.000000 [RGB] -> Lut -> 3.060566 -0.115180 1.191879 [Lab]
1 1 1
1.000000 1.000000 1.000000 [RGB] -> Lut -> 100.000000 -0.000062 0.000060
[Lab]
H:\bin> xicclu -ff -ir iPF6400-Canson-Baryta-310-i1Profiler-2584.icm
0 0 0
0.000000 0.000000 0.000000 [RGB] -> Lut -> 3.737745 0.015625 0.765625 [Lab]
1 1 1
1.000000 1.000000 1.000000 [RGB] -> Lut -> 100.000000 0.000000 0.000000
[Lab]
and the Bruce Lindbloom computed figures match the GamutVision DMax figures.
At this point it seems possible that the issue is with i1Profiler rather
than Argyll! I'll have to do some prints and check the blacks.
Are there any other tests that you can suggest to get to the bottom of this?
Regarding BetaRGB: I realize that it has a large gamut, but so does my
printer. I normally print using Relative so it isn't such an issue; when I
find that Perceptual gives a better result I use the smallest possible
working space. When I make a new profile I always check it with GamutVision
to make sure that there aren't any obvious problems and this is how I
noticed that there appeared to be a problem with the Argyll perceptual
profiles.
Robert
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