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

  • From: Nikolay Pokhilchenko <nikolay_po@xxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Thu, 18 Oct 2012 09:50:46 +0400

Thu, 18 Oct 2012 01:40:26 +0200 Xavi wrote:
>I have added a new column, with the deltaE 2000, on the xls file that I
>sent. Comparing deltaE00 with deltaeE76, I obtain lower values on deltaE00.
>With an average value of 3,95 using relative colorimetric intent and 7,08
>using the perceptual intent.
By deltaE You can actually check only the ablsolute colorimetric intent and 
only the colors in the printer gamut. By cheking the relative colorimetric 
intent You see white point adaptation dE between two media - standard and 
Yours. By checking perceptual intetnt by dE, You check the "artistic 
difference" which the profile introduces while gamut mapping transform. Both 
checks didn't show "quality" of the profile. They only shows the difference 
between media and difference of gamut mapping process. It's almost meaningless.

>I don't know if these are the values that I must obtain.
>Thank you very much.
>Best Regards,
>Xavier Puente.
>-----Mensaje original-----
>De: argyllcms-bounce@xxxxxxxxxxxxx [mailto:argyllcms-bounce@xxxxxxxxxxxxx]
>En nombre de Graeme Gill
>Enviado el: lunes, 15 de octubre de 2012 8:48
>Para: argyllcms@xxxxxxxxxxxxx
>Asunto: [argyllcms] Re: ArgyllCMS: shadow details and blue color issues.
>What I'm doing incorrectly?
>Xavi wrote:
>> 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.
>I'm guessing that the image you are using is from the DQ-Tool
>Monitor Reference File by Fujifilm Europe GmbH / Jens Rubb.
>If so, it's an unlabelled (ie. no colorspace) RGB file.
>The color of the "blue" fan bland is something like .09, .14, .55 RGB, so it
>is not a pure RGB blue, but is tending a little towards purple in the
>original, and all four of the soft proofs hint at this.
>> 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 can't verify this - the profile through perceptual seems very self
>consistent and neutral, ie:
>icclu -fb -ip Argyllv140_396parxes48Gris3Blanc.icm
>50.000000 0.000000 0.000000 [Lab] -> Lut -> 0.345472 0.388520 0.513978 [RGB]
>icclu -ff -ir Argyllv140_396parxes48Gris3Blanc.icm
>0.345472 0.388520 0.513978 [RGB] -> Lut -> 52.334969 -0.072152 -0.770024
>< 1 delta E hue & saturation error seems reasonable through a perceptual B2A
>It tends towards cyan as it nears the black point, due to Argyll's "extend
>and bend" neutral mapping.
>> 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_zps09f2fe
>> 42.jpg
>> On the other hand I see very natural colors, on the right image, 
>> softproofed using the same profile, but with the colorimetric intent.
>You soft proof does look somewhat reddish - but then I'm not sure how your
>softproof workflow is functioning. For instance, you are using BPC which
>could be having an effect on the neutrals, given the very non-neutral black
>point of your colorspace - ie. Argyll maintains neutrality down the neutral
>axis until it nears the black point, at which stage it becomes cyan tint, to
>match the black point. If the BPC then maps the cyan black to neutral with
>the mapping being in a straight line to the white point, then the neutral
>mid tones will get shoved in a megenta direction.
>Note that typical Argyll workflows won't use BPC and are not created to
>anticipate the effects of applying BPC, because you can do a more
>sophisticated mapping using the collink gamut mapping machinery. My typical
>softproof workflow is as follows:
># Create proofing transform from output to AdobeRGB collink -v -ila -G -qh
>-cpp -dmt Argyllv140_396parxes48Gris3Blanc.icm AdobeRGB1998.icm
># Create proof image back in AdobeRGB space cctiff
>Argyllv140_396parxes48Gris3Blanc_v.icm skin_sky_p.jpg skin_sky_pv.jpg
>The above softproof (not using BPC) doesn't show such a tint.
>> 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.
>I think a neutral black color will give better visual results, and leave
>less room for workflow details to affect the outputt.
>Graeme Gill.

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