[argyllcms] Re: something wrong in my workflow?

  • From: Graeme Gill <graeme@xxxxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Sun, 03 Jan 2010 12:02:13 +1100

Vallo Kallaste wrote:

iccdump -v3 -trXYZ -tgXYZ -tbXYZ 3008WFP-D65-2.2-smatrix.icm
    0:  0.149521, 0.635010, 0.091751    [Lab 83.705272, -161.137986, 75.722273]

There you go, the green primary has an a* value of -161, so it's outside the
ICC PCS encoding range of -128 to +128.

Althought I don't understand, the Lab space should represent all the human
visible colors?

It does, but the a* b* ranges are "unlimited", whereas the ICC encoding
ranges have to be practical, and therefore have limits.

[If you run the spectrum locus through the D50 conversion to L*a*b* you
 get many values that are outside the ICC PCS encoding range, depending
 on how far you push up or down the spectrum.]

I've got understanding that there is currently no consumer
technology available for representing all those colors? So there is only
two ways to interpret: I am wrong or my display is able to display some
imaginary green color :)

It's not imaginary, it's real (you can see it), it's just that it can't
be encoded in an L*a*b* PCS ICC profile. You can encode it in an XYZ PCS
ICC profile though.

This takes longer than I have patience for, stopped the process after 5
minutes. I don't have "state-of-the-art" system but quad-core Q9550@xxxxxx
should be still fast enough.

Sorry, I'm not sure quite what you're talking about.

Graeme Gill.

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