[argyllcms] Re: Display Calibration. Setting up RGBCMY Hue/Saturation controls.

  • From: Ivan Kadomin <ivan.kadomin@xxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Mon, 21 Mar 2011 17:56:54 +0300

The different WP with R=G=B=max settings means nothing alone.
You said you can achieve wider gamut with non-default custom mode settings, so R=G=B=100 doesn't necessarily result in a "native" WP. If one of them is a "native" WP then I think it is the Standard mode with R=G=B=255 because this one produces noticeably brighter output than Custom mode with R=G=B=100.
Standard with R=G=B=255 and Custom with R=G=B=100 and defaults for Hue/Saturation are not the same. But I found the following. If in the Custom mode you tune R, G and B to better correspond to native and measure their XYZ coordinates you will realise that they are very close to that of the Standard mode.

It looks like something like the following is going on (not exact numbers, just for understanding). Let's see the pure green patch chromaticity dependence (2nd column) on the G hue control position (1st column):
G_hcp    a^2+b^2
40    88
39    90
38    97
37    98
36    98
35    99
34    100
33    88
32    85
31    82
30    78

So, as you can see max. is at the pos. 34 and if you set G Hue control to this position (and repeat the same things for R an B) it will result to a gamut, which is a bit wider than in Standard. But as you can see 34 is sharp towards 33 and it is sloping towards 35 and far to 38. So that from 38 to 34 values are about the same. Taking into account possible parameters drift (voltages, luminophore aging, etc.) it may be safer to stay somewhere in the middle of this band for a stability reason, e.g. at 36. Once I changed 34 to 36, repeated the same for R and B and measured again XYZ for R, G and B for Custom and Standard, I found that they correspond to each other very well.
So, it looks like Standard is a kind of "stable" native.

So you didn't try to follow my all of my instructions?
Of course not. I'm not interesting in just the good final result. I'm interesting in "what" and "how" also. :))

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