[argyllcms] Re: CCSS not working?
- From: Graeme Gill <graeme@xxxxxxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Mon, 10 Aug 2020 23:22:16 +1000
johan@xxxxxx wrote:
Hi,
Are these based on the RGBW matrix calibration described in the paper below?
Yoshi Ohno and Steven W Brown, "Four-Color Matrix Method for Correction of
Tristimulus Colorimeters - Part 2",
Proc. of the IS&T Sixth Colour Imaging Conference, pp. 65-68 (1998)
No. a method that properly weights the result is better.
If so, they only work for additive displays. For displays with additional
colorants, such as RGBW or RGBY, this kind of calibration doesn't work.
No static colorimeter calibration will be accurate for a display
with variable spectral composition/separation. A 4D Lut with
an auxiliary input describing the extra channel state would
be needed.
If the separation is static, then in general a 3d Lut would be needed for
calibration, or if the separation is luminance independent,
then a 2d Lut would suffice.
Exactly the same considerations apply when considering using a colorimeter
to measure CMYK printing.
[ Of course all of the above is only of significance if the colorimeter
has a noticeable deviation from Standard Observer spectral sensitivity
curves. ]
Cheers,
Graeme Gill.
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