[argyllcms] Re: "RGB"-printer and inversion in blacks

  • From: Alexey Gribunin <Gribunin@xxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Tue, 24 Apr 2012 17:55:11 +0400

Hello Nikolay!

I think this strange behavior is because of the following issues of your device's dark area:
1) Quite dark R0,G0,B0 - L=3.7, a=-0.65, b=-3.6.
2) At the same time the darkest neutral point is quite light - approximately L=10.

I don't think you want to use this device as color proofing device, right?
So I suppose that in this case you don't need good colorimetric precision, you need just good visual quality.

So I would try to edit measurements to make it more "correct". I would try to "move" darkest point R0,G0,B0 from L=3.7, a=-0.65, b=-3.6 to L=3.7, a=-0.65, b=0. Certainly, in such case it's necessary to "move" some neighbor values too e.g. by using some linear equation.

By using this method, I think, you will get more deep and correct shadows. Such small blue cast in such deep shadows will be invisible, for sure.

Best regards,
Alexey Gribunin, UNIT Color Technologies, Moscow, Russia.

On 24-04-12 14:04, Nikolay Pokhilchenko wrote:
Hello, Graeme.
Can You take a look on the device (TI3 attached in archieve)?
Perceptual and Saturation intents in ArgyllCMS profile are OK, but
relative intent is quite strange: there is lightness inversion at the
black side of a gray gradient.
I know that the device is behaved bad. But I didn't expecting that there
will be lightness reverse at a black side. See the boxes below the 8..18
numbers in Test_relative.png attachment. It seems that the black point
is lighter than some intermediate dark gray.
I'm searching a way how to achieve a uniform gradient with relative intent.

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