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Calculating Color temperature and Color Rendering Index..

by R33E8
Tags: color, index, rendering, temperature
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Mar19-09, 08:10 AM
P: 3
Hi, I've been a lurker here for a while but I finally have a question. I was wondering if there is a simple formula to calculate the Color Rendering Index(CRI) and Correlated Color Temperature(CCT) of a white light source.. To do this I would also need (I think) to make a some points on a chromacity diagram. Right now, all I have is the wavelength emissions of the light in an excel spreadsheet... So basically, I want to know how to convert from wavelength emissions, to a chromacity diagram, to CRI and CCT.. I've looked quickly for some software to do this but it was $1000.... Thanks..
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Andy Resnick
Mar19-09, 12:00 PM
Sci Advisor
P: 5,517
Interesting question. I think you first need to generate the CIE coordinates for your source. Has a few calculations, and has another procedure. Has some free uilities.

Good luck- this should be a good learning excersise (meant unironically).
Apr7-09, 04:46 PM
P: 2
You will like this tool:
It's a free program and if I remember correctly allows you to load in your own spectrum (which I think you have, judging from your info) and do some color calculations on it.

Otherwise the abovementioned links, coupled with this one should provide you with the answers. It is not as hard as it looks :)

Apr15-09, 11:26 AM
P: 3
Calculating Color temperature and Color Rendering Index..

Thank you both so much! These links really helped (especially the color calculator, thanks Kelemvor)!
Oct11-10, 10:40 PM
P: 2
did anybody have the calculator from this link?

I can't open this site link, so if anybody can send me this program, it would be very appreciated.

Oct11-10, 10:50 PM
P: 2
my mail address is, Thanks!
Nov3-10, 07:58 AM
P: 2
You can find it here now. They changed their main webaddress.
Jun24-11, 10:20 AM
P: 2
Hi Folks,
I am trying to use color calculator software in order to calculate color and coordinates for my own SPD (Intensity vs wavelength curve). Would you please let me know how to upload my graph into color calculator program. It does give me some instructions bout it is not clear to me if I have to save an data file in the color calculator folder. Any info is highly appreciated. Thanks
Jun24-11, 03:41 PM
P: 2
Would you guys know the availability of a free software to calculate CRI for a given SPD curve and direct it to me. Thanks
May28-13, 01:03 AM
P: 1
Hello all.

I realize this is quite an old post, but if anyone has stumbled upon this thread because they have use for spectral analysis and/or composition, please check out the ColorTools package available on the LabVIEW Tools Network. A thorough description and trial of the package are available here: . In addition to a LabVIEW Toolkit, we have executables available for use with LabVIEW RunTime.

The package will calculate all CIE (xy, uv) color coordinates, CRI, CQS, as well as generate xy and uv color plots, color gamut, Planckian locus, and many many more features necessary for describing and analyzing color.

Please feel free to contact me directly here or at

Kind Regards,

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