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

  • From: Graeme Gill <graeme@xxxxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Fri, 18 Mar 2011 12:27:28 +1100

Ivan Kadomin wrote:
settings are available only. In "Custom Colors" in addition to RGB Gain
and RGB Bias controls there are RGBCMY Hue/Saturation controls.

OK, on thinking about this a little more, I have a more refined

I gather each primary has a Saturation and Hue setting.

What I'd try would be to:

  Set all the saturation controls to 100% or Maximum.

  Using dispwin & spotread, adjust the hue of R, G & B in turn
  to maximize chroma, ie. maximize a^2 + b^2, or even |a| + |b| may
  be sufficient guide. [ The aim is to put the fake RGB primaries right
  in the corners of the real native RGB triangle. ]

  Measure the Yxy for each of R, G & B.

  Compute the interpolated xy for the C, M & Y primaries from
  the R,G & B xy. (ie. Cx = (Gx + Bx)/2, etc.)

  Adjust the C, M & Y hues to have an xy closes to your computed xy.

  [ The aim is to make C, M & Y the natural linear combination of the
    real primaries. ]

(This all assumes that the controls place the fake primaries on the
 edge of the native gamut boundaries, and don't put them outside
 that boundary and clip.)

Unless they are actually implemented in hardware rather than simply
changing lookup tables, the RGB Gain and RGB Bias controls should probably
be set to "do nothing" settings, although it's probably worth a fiddle
to see what they actually do.

Graeme Gill.

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