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 Author Topic: Pantone Huey for monitor calibration?  (Read 21493 times)
Doug Kerr
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Hi, gang,

This is mostly an excuse to say hello! I just joined this floating crap game!

Please be patient while I learn how to function in this joint!

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Looks like it yes. Optix XR Pro shows x=.313 and y=.329 and a CCT of 6504.
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x=.313, y=.329 explicitly defines a chromaticity. That chromaticity (presumably, from what you say) has a CCT of 6504K, as do an infinite number of other chromaticities.

So the CCT is not another coordinate, but merely a "property" of the chromaticity that is completely defined by the x and y coordinates (conveniently delivered to us by that program, evidently).

As has been well covered in this thread, the CCT does not define a unique chromaticity, nor is it needed (in conjunction with x and y) to define one.

Best regards,

Doug
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Best regards,

Doug

Visit The Pumpkin, a lbrary of my technical writings:
http://doug.kerr.home.att.net/pumpkin

"Make everything as simple as possible, but no simpler."
Doug Kerr
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A cct by definition is a point ON the planckian locus or BBRC.
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Actually, a CCT is just a number. It is not a point on the x-y plane, on the Planckian locus or otherwise.

But if you "ask for" the chromaticity whose CT (not CCT) is that CCT value, then you have a particular point on the Planckian locus (and thus a specific chromaticity).

If you ask for "something" whose CCT is that value, you get an iso-temperature line.

Best regards,

Doug
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Best regards,

Doug

Visit The Pumpkin, a lbrary of my technical writings:
http://doug.kerr.home.att.net/pumpkin

"Make everything as simple as possible, but no simpler."
Serge Cashman
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Thanks for that article. It is very informative.

What's important for calibration purpouses is that both D65 and 6500K when used by calibration software as white point targets refer to specific cromaticities, with defined coordinates.

However if you get a Native white point of a monitor and want to calibrate another monitor to the same target you do need to use the x and y CIE coordinates and not the K number, which corresponds to infinite number of chromaticities like you said.
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opgr
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Hello Doug,

Welcome to the forums.

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Actually, a CCT is just a number. It is not a point on the x-y plane, on the Planckian locus or otherwise.

But if you "ask for" the chromaticity whose CT (not CCT) is that CCT value, then you have a particular point on the Planckian locus (and thus a specific chromaticity).

If you ask for "something" whose CCT is that value, you get an iso-temperature line.
With all due respect, but do you really think that this nitty-gritty word-game is a useful contribution to the discussion? I believe that Serge's conclusion clearly shows his understanding of the concepts and the corresponding ambiguities.

And again, you are also reversing the logic:

[geek warning on]
If you have a chromaticity of a selective radiator that is not equal to any of the chromaticities of the blackbody radiator, then the CCT is defined as the temperature of the blackbody radiator whose perceived color most closely resembles the perceived color of the selective radiator.

This is almost verbatim from Wyszecki & Stiles, which I presume is still the reference for this subject.
[geek warning off]

In normal language: if you have a color close to the planckian locus, then the CCT is the closest color ON the planckian locus. PERIOD.

Obviously, no software (or scientist) is going to ask for a CCT as opposed to a CT, and then pick a random color on the iso-temperature line. Although given the wildly varying results of current software offerings, one would be inclined to think they actually do pick a random number... (joke).
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Regards,
Oscar Rysdyk
theimagingfactory
Doug Kerr
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Hello Doug,

Welcome to the forums.
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Thank you, Oscar. This looks like a really good place.
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Best regards,

Doug

Visit The Pumpkin, a lbrary of my technical writings:
http://doug.kerr.home.att.net/pumpkin

"Make everything as simple as possible, but no simpler."
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