[argyllcms] Re: Argyll DeviceLinks under CC lic / Blackgeneration
- From: Gerhard Fuernkranz <nospam456@xxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Sun, 03 Feb 2008 19:00:58 +0100
Jan-Peter Homann wrote:
> Hello list,
> I did some tests, with profile Gerhard made for me to limit the TAC of
> FOGRA39 data.
> It is making a good job, very smooth rendering, preserving separation
> and correct limiting of the TAC (What is not possible with X-Rite
> High-End Profilemaker devicelink module)
>
> I think to render a handful of profiles for some standards (FOGRA,
> GRACoL, SWOP, IFRA...) would be helpful projekt.
>
> For this profile is still one feature missing, to play in first league
> of devicelinking products. This is the preservation of the pure blacks.
> In the testprofile for FOGRA39 / ISOcoated generated with:
>
> icclink -v -qh -kt -l300 -L95 -G -ir -cpp -dpp ISOcoated_v2_eci.icc
> ISOcoated_v2_eci.icc link.icc
>
> pure plack is preserved form 0 to 85 and then, CMY is added for the
> darker colors leading to C47 M38 Y38 K100
>
> I guess, that this is caused by the parameter -L95. Which limits Black
> to the max of 95 even for pure blacks.
>
> Gerhard, could You plaese make a seconsd profile with -L100 (or will
> we gat the same result by just don´t specifying this parameter ?)
> Please name this profile "LimitTAC300_coatedFOGRA39_argyll.icc"
Jan-Peter,
I built a new one with -L100, and as far as I have checked, this one now
preserves the black as expected.
$ icclu LimitTAC300_coatedFOGRA39_argyll.icc
0 0 0 0
0.000000 0.000000 0.000000 0.000000 [CMYK] -> Lut -> 0.000000 0.000000
0.000000 0.000000 [CMYK]
0 0 0 .1
0.000000 0.000000 0.000000 0.100000 [CMYK] -> Lut -> 0.000000 0.000000
0.000000 0.099997 [CMYK]
0 0 0 .2
0.000000 0.000000 0.000000 0.200000 [CMYK] -> Lut -> 0.000000 0.000000
0.000000 0.199994 [CMYK]
0 0 0 .3
0.000000 0.000000 0.000000 0.300000 [CMYK] -> Lut -> 0.000000 0.000000
0.000000 0.299991 [CMYK]
0 0 0 .5
0.000000 0.000000 0.000000 0.500000 [CMYK] -> Lut -> 0.000000 0.000000
0.000000 0.500000 [CMYK]
0 0 0 .8
0.000000 0.000000 0.000000 0.800000 [CMYK] -> Lut -> 0.000000 0.000000
0.000000 0.800006 [CMYK]
0 0 0 .85
0.000000 0.000000 0.000000 0.850000 [CMYK] -> Lut -> 0.000000 0.000000
0.000000 0.849989 [CMYK]
0 0 0 .9
0.000000 0.000000 0.000000 0.900000 [CMYK] -> Lut -> 0.000000 0.000000
0.000000 0.900003 [CMYK]
0 0 0 .95
0.000000 0.000000 0.000000 0.950000 [CMYK] -> Lut -> 0.000000 0.000000
0.000000 0.949986 [CMYK]
0 0 0 1
0.000000 0.000000 0.000000 1.000000 [CMYK] -> Lut -> 0.000000 0.000000
0.000000 1.000000 [CMYK]
Was possibly not a good idea to adopt the -L95 from the ISOcoated_v2_eci
profile. But I'm still wondering, why the device link created with -L95
started limiting already at 85 and not at 95.
This time I also used "-ia" in order that icclink does not establish a
gamut mapping, which I guess might introduce additional inaccuracies
too? Since source and destination white points are the same in this
particular case, absolute should give the same result as relative
colorimetric.
Graeme,
is there a reason why icclink -G does not support a relative
colorimetric intent without gamut mapping (similar to -ia, but relative)?
Regards,
Gerhard
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