[argyllcms] Re: ArgyllCMS: shadow details and blue color issues. What I'm doing incorrectly?

  • From: "Xavi" <aruiz@xxxxxxxxxxx>
  • To: <argyllcms@xxxxxxxxxxxxx>
  • Date: Wed, 10 Oct 2012 19:28:53 +0200

Hello Graeme.

Thank you for your kind and instructional reply.

"It's always hard to investigate such issues without all the details of the
workflow and being able to examine the resulting print, but at least in the
softproof simulations of the profile, I'm not sure I can really reproduce
this. While the perceptual profile (as expected) has slightly less saturated
blues (see <http://www.argyllcms.com/RGBsurfall_pv.tif> than the
colorimetric intent (see <http://www.argyllcms.com/RGBsurfall_rv.tif>,
they are not what I'd call washed out, and the neutrals are not obviously
tinted."

On my case the softproof and the print are very very similar. On prints,
using perceptual intent, I see the blue color as a light purple color, as I
see on the screen when I softproof with Photoshop CS6. Also checked on
prints with 2 models of spectros using spot read.

Also the overall color is changed to a magenta cast, when I use perceptual
intent. Using the saturation intent the blue color is less purple color and
is more vivid but skin colors, for example, are more reddish and excessive
saturated.

I have created a collage with 3 cropped photos. Please, tell me if you see
the reddish/magenta cast on color skin. And also, if you agree with me that
the blue color of the sky, seems a blue/purple very light and not saturated:

http://i436.photobucket.com/albums/qq82/aaruizz/prcptualvsRC_zps09f2fe42.jpg

On the other hand I see very natural colors, on the right image, softproofed
using the same profile, but with the colorimetric intent.

In my case, I don't see the blue color that you show me on your link:
<http://www.argyllcms.com/RGBsurfall_pv.tif>, when I use perceptual intent.
If for you is  a reference the "Rainbow Granger" image, I can't send you a
JPG of the results of softproofing it.

I think that my workflow is correct because if it was not correct, I
suppose, that it can't show  the overall colors, so correctly, using the
relative colorimetric intent.

I am doing all the profiles with a Canon Pro9000MKII with third party inks
(Hobbicolors UW). I will do,  from zero, new profiles for another Canon
MP540, that uses only four different color cartridges (CMYK) and also I will
start creating profiles, from zero, for the Pro9000MKII but using cartridges
refilled with other third party ink (OCP), that uses a very neutral black
color but that their gamut is more limited vs Hobbicolors Ultra Wide Gamut
inks.

Then I could recheck all the process and also see better blacks, using
relative colorimetric intent, because OCP inks has a neutral black.
Hobbicolors inks has a brown greys and blacks, when ptinting without a
custom profile, that confirm what you say in reference to a not deeper
blacks with relative colorimetric intent: "That's a consequence of the
device having a very non-neutral black point, and it being a colorimetric
intent."


"In contrast, the perceptual mapping makes more effort to map the neutral
axis and luminance ranges. You could try a "la" - Luminance axis matched
Appearance intent for the perceptual table (-t la)as a compromise between
the two. Another option is to use one of the two saturation intents, which
should give good blacks and more saturated (and possibly darker) blues."

I have tried the "-t la" option and, only to test, plenty of -T and -t
options with no better results.


"I'm quite seriously thinking of changing the documentation for the "-q"
flag:

-q fmsu         Speed - Fast, Medium (def), Slow, Ultra Slow

to try and dissuade people from "turning it up to 11" without good reason.
(<http://en.wikipedia.org/wiki/Up_to_eleven>).
Your device seems reasonably well behaved, and I would think needs no more
than -qm, or -qh at the most."



Thank you for the wikipedia link because I never imagined what means
"turning it up to 11".LOL.
As you recommend I will make the profiles using the "-q m" or the "-q h"
option.

I go start refilling a set of cartridges with OCP ink and I will create and
print the patches with the Pro9000MKII and with the MP540 and if you agree,
I will post the results of the softproof with each one.

Thank you a lot for your interest and time spent in my case.

Best Regards,
Xavi.




 

-----Mensaje original-----
De: argyllcms-bounce@xxxxxxxxxxxxx [mailto:argyllcms-bounce@xxxxxxxxxxxxx]
En nombre de Graeme Gill
Enviado el: miércoles, 10 de octubre de 2012 14:41
Para: argyllcms@xxxxxxxxxxxxx
Asunto: [argyllcms] Re: ArgyllCMS: shadow details and blue color issues.
What I'm doing incorrectly?


Hi,

> The results were not acceptable when I use the perceptual intent due 
> to a very muted or washed blue color and a slight magenta cast. Blacks are
deeper blacks.

It's always hard to investigate such issues without all the details of the
workflow and being able to examine the resulting print, but at least in the
softproof simulations of the profile, I'm not sure I can really reproduce
this. While the perceptual profile (as expected) has slightly less saturated
blues (see <http://www.argyllcms.com/RGBsurfall_pv.tif> than the
colorimetric intent (see <http://www.argyllcms.com/RGBsurfall_rv.tif>,
they are not what I'd call washed out, and the neutrals are not obviously
tinted.

Note though that it depends to some degree what you are looking for.
The nature of a print device is that there is a severe trade-off between
saturation and lightness in blue. The Perceptual intent (by the tuning I've
chosen) is lighter and less saturated than the clipping of the colorimetric
intent, and (to my taste) is visually closer to the very intense and light
color of the source AdobeRGB blue (Helmholtz-Kohlraush effect). The
colorimetric reproduction is certainly more saturated, but is overly dark in
my opinion.

> If I print using the same profile, and the same paper, but using the 
> relative colorimetric intent, the blue color is perfect (not washed or 
> muted), but the blacks are more dark greys than blacks. Also I loose the
shadow detail.

That's a consequence of the device having a very non-neutral black point,
and it being a colorimetric intent. "Colorimetric" strictly implies point by
point absolute minimum color error, and the shortest distance from the
target of perfect black to the gamut surface is dark blue/grey. A darker
mapping would have a higher saturation error, and a higher total delta E.
In contrast, the perceptual mapping makes more effort to map the neutral
axis and luminance ranges. You could try a "la" - Luminance axis matched
Appearance intent for the perceptual table (-t la)as a compromise between
the two. Another option is to use one of the two saturation intents, which
should give good blacks and more saturated (and possibly darker) blues.

> Thinking that I will improve blacks and shadow details on relative 
> colorimetric, I have do charts with more patches: 396 patches with 48 
> greys and 3 whites, 1188 patches with
> 128 greys and 3 whites and 1980 patches with 256 greys and 3 whites.

Since the black is a result of the device behaviour near black and the
intent, increasing the number of patches is not likely to change anything.

> *colprof -v -qu -iD50 -o 1931_2 -S AdobeRGB1998.icc -cmt -dpp
-D"Description Profile"
> -O"NameProfile.icm" Argyllv140_396parxes48Gris3Blanc

I'm quite seriously thinking of changing the documentation for the "-q"
flag:

-q fmsu         Speed - Fast, Medium (def), Slow, Ultra Slow

to try and dissuade people from "turning it up to 11" without good reason.
(<http://en.wikipedia.org/wiki/Up_to_eleven>).
Your device seems reasonably well behaved, and I would think needs no more
than -qm, or -qh at the most.

Cheers,

Graeme Gill.



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