Re: D vs K
Re: D vs K
- Subject: Re: D vs K
- From: Sven Westerlund <email@hidden>
- Date: Sat, 25 Jan 2003 20:32:03 +0100
Excellent and very comprehensive!
But sorry...
I can't take this out to my clients.
I understand BL within this "So a spectrum is very precise and unique. Its xyY
is less precise and
unique. Its correlated color temperature is even less precise and unique.
If I explain the Max Planck equation nr 1: Mc= cL-5( ecs/LT-1)-1 (you can't see
the right figures her)
as: "... the maximum theoretical energy that can be emitted at any wavelength
at
a given temperature." they'll give up!
The reason for my first question was this confusion:
Why does several(most) monitor-cal.software give you these choices:
"D65, D50, 6500K, 5000K or whatever colortemp. you want"
The latest MWU-report also talks about "the desired whitepoint of D65"
But can you really achive that on a monitor?
I've adopted Don Hutchesons method for tuning workflow
and softproofing, and it gives me extremely good results.
And what's his statement?
"Calibrate your monitor to the colortemp. and brightrness that matches your
D50 viewinglight"
So, I'll give you a leading question/statement:
"I calibrate my monitor to a colortemp. in K, that matches my CIE D50-standard
viewingbox"
Am I right?
Yours
Sven Westerlund
Stockholm Sweden
"Bruce J. Lindbloom" wrote:
>
Sven Westerlund wrote:
>
> What4s the different between D65 and 6500K(or D50 and 5000K)
>
>
D65 is a spectral power distribution, or SPD (i.e. a certain amount of
>
energy wavelength by wavelength across the visible spectrum). This spectrum
>
may be calculated for any correlated color temperature using formulas and
>
tables published by the CIE. You plug 6500 into the formulas and out pops
>
the D65 SPD. This is a jagged looking spectrum.
>
>
A blackbody radiator whose temperature is 6500 degrees Kelvin emits an SPD
>
which may be calculated using Planck's formula. Plug in 6500 and out pops
>
the blackbody SPD. This is a smooth spectrum, but generally similar to the
>
D65 SPD.
>
>
(You may graphically view these and other spectra here:
>
<http://www.brucelindbloom.com/CIESpectralCalculator.html>.)
>
>
Any spectrum, when "viewed" with the CIE standard observer functions,
>
produces XYZ or xyY.
>
>
There are many different spectra that can produce the same xyY (a
>
many-to-one mapping). So given a spectrum, you can determine its xyY, but
>
given an xyY, you cannot determine its spectrum.
>
>
Most xyY colors can be expressed as a "correlated color temperature" which
>
is determined by finding the temperature of a blackbody radiator whose color
>
is "closest" to it. There are many different xyY colors that have the same
>
correlated color temperature (another many-to-one mapping). So given an xyY,
>
you can determine its correlated color temperature, but given a correlated
>
color temperature, you cannot determine its xyY (nor its spectrum as just
>
mentioned).
>
>
So a spectrum is very precise and unique. Its xyY is less precise and
>
unique. Its correlated color temperature is even less precise and unique.
>
>
Getting back (finally) to the original question, D65 is a unique SPD (there
>
exists only one). A color whose correlated color temperature is 6500K is not
>
unique (there are infinitely many different xyY and SPDs that share it).
>
>
How's that for a long answer to a short question?
>
--
>
Bruce J. Lindbloom
>
email@hidden
>
http://www.brucelindbloom.com
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| | >Re: D vs K (From: "Bruce J. Lindbloom" <email@hidden>) |