[argyllcms] Re: ArgyllCMS: shadow details and blue color issues. What I'm doing incorrectly?
- From: "Xavi" <aruiz@xxxxxxxxxxx>
- To: <argyllcms@xxxxxxxxxxxxx>
- Date: Wed, 24 Oct 2012 02:06:02 +0200
Hi Graeme.
"Without knowing the workflow of how those colorchecker values made their
way to the print (ie., measured colorchecker values reproduced using
absolute colorimetric reproduction ?), I'm not sure this leads anywhere."
I don't know if you are refering to my print workflow or to the workflow to
obtain the measured values of the ColorChecker chart.
I do obtain the values of the simulated colorchecker simply positioning the
mouse over the color patch, and PS informs me of the Lab values of the
patch. It is not important wich colors has the colochecker chart. I can use
different colors. The important think is that I have the Lab values of the
source colors to compare, using the spectro, with the printed colors.
I print these patches with PS using the media settings used to create the
test chart, selecting the profile created with ArgyllCMS and with the
absolute colorimetric rendering intent.
If you use or you think that there is a good alternative to print, under
Windows, instead of PS, please tell me the name of the application and then
I will try it.
I have two Canon printers. I read, some time ago, that is not posible to
disable totally, the color management, on Canon drivers despite select the
option "Matching None" on the menu option "Manual color management".
Then I am trying to confirm that when I print, I obtain the expected
results.
If I understand correctly, I think that what you explain me here:
"It's far better to directly check critical spot colors against the profile.
For instance, pick a neutral color (say Lab 50,0,0), then look it up using
the absolute colorimetric B2A table, then print that RGB value using the
same print path as the test chart. Measure it. Check the delta E against the
target. etc."
Is what I'm looking for to confirm that the results on paper are the
expected.
But, please, permits me to confirm that the steps that I have did, are
correct:
I have picked your proposed neutral color and three more colors.
.\icclu -fb -ia -s255 MP_B01_A4_HPEv
erydayBrilloIIQ1Dif_NoVPre_396p64g3bArgyllv140_121011Opcio_qm_ACPU.icm
50
50.000000 0.000000 0.000000 [Lab] -> Lut -> 145.867671 129.040916 161.476401
[RGB]
.\icclu -fb -ia -s255
MP_B01_A4_HPEverydayBrilloIIQ1Dif_NoVPre_396p64g3bArgyllv140_121011Opcio_qm_
ACPU.icm
29 14 -50
29.000000 14.000000 -50.000000 [Lab] -> Lut -> 52.419577 73.171278
212.637893 [R
GB]
82 4 80
82.000000 4.000000 80.000000 [Lab] -> Lut -> 242.404058 222.659529 84.345080
[RGB]
38 14 14
38.000000 14.000000 14.000000 [Lab] -> Lut -> 144.295692 79.603775 69.836974
[RGB]
Then, on Photoshop I create 4 rectangles, that I fill, one by one, with the
RGB values obtained. I save them on Tiff format and I print the file with
the same program and the same printing options that I have used to print the
test chart.
For example, If I have used PS CS4 (that prints without color management) to
print the test patches then I print too the Tiff file with the 4 patches
also without color management.
After, I must to let them to dry and read them with the spectro.
There are some hours that the printed patches are drying but I prefer to let
dry overnight. The impatience have make read the patches with the results
that I attach you on a XLS. Average dE76: 5,13 . Average dE00: 1,95
Please could you confirm me that the steps that I have explained are
correct? If yes, the results of the deltaE are the expected?
If the steps that I have do and the results are correct, then I will test
the "xicclu -fif".
Thank you very much for your help.
Best Regards,
Xavi.
-----Mensaje original-----
De: argyllcms-bounce@xxxxxxxxxxxxx [mailto:argyllcms-bounce@xxxxxxxxxxxxx]
En nombre de Graeme Gill
Enviado el: lunes, 22 de octubre de 2012 9:33
Para: argyllcms@xxxxxxxxxxxxx
Asunto: [argyllcms] Re: ArgyllCMS: shadow details and blue color issues.
What I'm doing incorrectly?
Xavi wrote:
> Dear Graeme.
>
> I enjoy reading your replies although I discover that my knowledge of
> color management is very basic.
>
> All the images that I use to test the printer profiles, are mainly
> labelled with the AdobeRGB and the others with the sRGB color spaces.
> Then, seems that this is not the reason of color change.
>
> As I commented to you, I have changed all the cartridges of my
> Pro9000 to use another brand of ink, to have more chances to discover
> what is happening. Then I can't use at this moment, the printer with
> the ink of the example of ICM that you used in your icclu example
> (Argyllv140_396parxes48Gris3Blanc.icm).
>
> I must to use the MP540 printer with the
> "MP_B01_A4_HPEverydayBrilloIIQ1Dif_NoVPre_396p64g3bArgyllv140_121011Op
> cio_qm _ACPU.icm". Sorry to the extent name, but I have created a lot
> of profiles and the name was growing trying to identify them.
>
> I have do the same example, than you show me, using this ICM:
>
> .\icclu -fb -ip
> MP_B01_A4_HPEverydayBrilloIIQ1Dif_NoVPre_396p64g3bArgyllv140_121011Opc
> io_qm_
> ACPU.icm
> 50
> 50.000000 0.000000 0.000000 [Lab] -> Lut -> 0.563818 0.500477 0.630465
> [RGB]
>
> .\icclu -ff -ir
> MP_B01_A4_HPEverydayBrilloIIQ1Dif_NoVPre_396p64g3bArgyllv140_121011Opc
> io_qm_
> ACPU.icm
> 0.563818 0.500477 0.630465
> 0.563818 0.500477 0.630465 [RGB] -> Lut -> 52.109114 0.326121
> -0.977612 [Lab]
Hi,
> I don't know if the reading with an spectro some patches, is a good
> way to show you what I obtain on prints but I have print a simulation
> of the patches of a colorchecker card and I have read the results with a
spectro.
Without knowing the workflow of how those colorchecker values made their way
to the print (ie., measured colorchecker values reproduced using absolute
colorimetric reproduction ?), I'm not sure this leads anywhere.
It's far better to directly check critical spot colors against the profile.
For instance, pick a neutral color (say Lab 50,0,0), then look it up using
the absolute colorimetric B2A table, then print that RGB value using the
same print path as the test chart. Measure it. Check the delta E against the
target.
etc.
You can also then check the profiles self consistency. How much different is
the relative colorimetric B2A for a given neutral color compared to xicclu
-fif ?
[Note - an instrument measurement by default will correspond to absolute
colorimetric rendering intent. ]
If the colorimetric model of the profile matches the device reasonably well,
then you can look into the behaviour of the perceptual rendering (as I was
doing using the icclu).
> Applyiing the icclu example that you show me to the values of blue
> color
> patch:
>
> .\icclu -fb -ip
> MP_B01_A4_HPEverydayBrilloIIQ1Dif_NoVPre_396p64g3bArgyllv140_121011Opc
> io_qm_
> ACPU.icm
> 28.87 14.81 -50.15
> 28.870000 14.810000 -50.150000 [Lab] -> Lut -> 0.358232 0.399245
> 0.879326 [RGB]
>
> .\icclu -ff -ir
> MP_B01_A4_HPEverydayBrilloIIQ1Dif_NoVPre_396p64g3bArgyllv140_121011Opc
> io_qm_
> ACPU.icm
> 0.358232 0.399245 0.879326
> 0.358232 0.399245 0.879326 [RGB] -> Lut -> 39.085966 11.557139
> -49.964686 [Lab]
>
> I must obtain, on paper and with perceptual intent, a patch with 39.09
11.56
> -49.96 Lab values, but I read a patch with 39,35 4,45 -48,45 Lab
> values. That's a deltaE76 of 11,77.
It's not that reasonable to be looking at delta E's of non-neutral colors
for perceptual rendering, unless you really understand what's going on.
By definition it is not colorimetrically accurate - it aims at a pleasing
reproduction that tries to preserve the look of the original (ie. not
clipping) while staying within gamut.
Graeme Gill.
Other related posts:
