[argyllcms] Re: XYZ and wavelength interval
- From: <Skyforce.Shen@xxxxxxx>
- To: <argyllcms@xxxxxxxxxxxxx>
- Date: Wed, 30 Jun 2010 11:43:25 +0800
Dear Matthieu:
You should modify CIEXYZ formulas like below:
X = SUMPRODUCT( "CubicSplineTransformedData" ; "StandartObserverx" )
* 5 * .683002
Y = SUMPRODUCT( "CubicSplineTransformedData" ; "StandartObservery" )
* 5 * .683002
Z = SUMPRODUCT( "CubicSplineTransformedData" ; "StandartObserverZ" )
* 5 * .683002
The number 683 is connected to the modern (1979) definition of the candela
<http://en.wikipedia.org/wiki/Candela> , the unit of luminous intensity
<http://en.wikipedia.org/wiki/Luminous_intensity> . (reference from
http://en.wikipedia.org/wiki/Luminosity_function)
FYI.
Skyforce Shen
Electronic System Div.
Project Team IV,RSEE4
AU Optronics Corporation
No.23 Li-Hsin Rd.
Hsinchu Science Park
Hsinchu 30078, Taiwan, R.O.C.
Tel: +886-3-500-8800 Ext. 6304
Fax: +886-3-567-9036
skyforce.Shen@xxxxxxx
AUO.com <http://auo.com/>
From: argyllcms-bounce@xxxxxxxxxxxxx [mailto:argyllcms-bounce@xxxxxxxxxxxxx] On
Behalf Of Matthieu DUBAIL
Sent: Wednesday, June 30, 2010 9:42 AM
To: argyllcms@xxxxxxxxxxxxx
Subject: [argyllcms] Re: XYZ and wavelength interval
Hi Keith,
Thank you for the answer.
I'm still not able to get the same results as Argyll.
Here is how I did the measurement and calculation:
1. Measured with colormunki ang Argyll using -H option for high definition
spectral measurement (from 350nm to 750nm every 3,33nm)
2. Used cubic spline to transform the spectral datas from 380nm to 730nm every
5nm
3. Picked up the 5nm CIE 2° standart observer.
4 Calculated the XYZ using the following formulas on Excel:
X = SUMPRODUCT( "CubicSplineTransformedData" ; "StandartObserverx" )
* 5
Y = SUMPRODUCT( "CubicSplineTransformedData" ; "StandartObservery" )
* 5
Z = SUMPRODUCT( "CubicSplineTransformedData" ; "StandartObserverZ" )
* 5
I'm getting:
X = 63,5
Y = 67,66
Z = 69,36
While Argyll gives me:
X = 43,37
Y = 46,21
Z = 47,37
What am I doing wrong?
I attached spectral graphic file on how cubic spline perform and standart
observer used (normalise at 555nm).
I fear once I answered this question, I might have a few more on phototometric
(Lux and Guide number calculation) and radiometric (Joule calcultation) to
ask.......
Thank you by advance,
Matthieu DUBAIL
www.presse-bouton.com
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