[argyllcms] Re: Getting mediocre D-max with Canon iB4020 pigment printer profiles. Operator error?
- From: Graeme Gill <graeme@xxxxxxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Fri, 9 Jun 2017 14:36:31 +1000
ldasignup@xxxxxxxxx wrote:
Hi,
I’m disappointed that the darkest blacks (D-Max) from my Canon iB4020 CMYK
pigment
printer with Argyll-CMS profiles are darker. Am I doing something wrong?
With the Maxify iB4020 using Canon ink and Canon paper, the ACPU black
(0,0,0) patch
and
corresponding (0,0,0) patch from test prints made with that profile have been:
ACPU PhotoShop
GP-601 Glossy: L = 10.77 L = (16.2 – 16.7)
Luster: L = 4.89 L = (9.2 – 9.7)
Plus Glossy II: L = 5.30 L = (11.8 – 12.7)
Platinum: L = 5.72 L = 12.8 – 13.1)
SemiGloss: L = 5.78 L = 11.3 – 12.7)
The above seems to indicate that the printer + ink + paper is capable of
relatively
deep blacks when printing is done by ACPU with no profile, but those blacks
aren’t
being realized with the profile in use.
Note that I have tried checking if there was a difference with the PS option
“Black
Point Compensation” that that didn’t seem to matter.
There are two aspects to this, one is the profile contents, and the other is
the manner in which the application is using it.
Using the .ti3 file you sent me, I see the black patch has
Lab 5.72 -0.71 -6.74
Making a profile from this using:
colprof -v -qh CurTi3
I see:
icclu -ff -ia CurTi3.icm
0.000000 0.000000 0.000000 [RGB] -> Lut -> 5.913043 -0.781276 -6.843825 [Lab]
which seems reasonable, and round tripping the B2A table gives:
icclu -fb -ia CurTi3.icm
5.913043 -0.781276 -6.843825 [Lab] -> Lut -> 0.005658 0.007215 0.000381 [RGB]
icclu -ff -ia CurTi3.icm
0.005658 0.007215 0.000381 [RGB] -> Lut -> 7.016849 -1.726478 -6.933478 [Lab]
which doesn't seem to bad either, given the limitations of the resolution of a
B2A
table near its edges. (Note that a device link workflow will have better
accuracy
in this regard).
Putting in Lab 0,0,0 gives:
icclu -fb -ia CurTi3.icm
0.000000 0.000000 0.000000 [Lab] -> Lut -> 0.000000 0.000000 0.000000 [RGB]
i.e. the colorimetric B2A table is clipping to device black.
So the question for you is what is your CM setup for Photoshop ?
i.e. what source colorspace and what intent are you using ?
Is BPC on or off ?
Cheers,
Graeme Gill.
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