Is there a way to convert color specifications defined by N.B.S. units in x, y, Y color space under illuminant C, 2° Standard Observer to delta E* values in CIE L*a*b* color space under D65, 10° Standard Observer? I have been unable to find a mathematical conversion due to the difference in illuminant and Standard Observer function.
Hello Mam,
from my knowledge i would like to suggest you to please go through the attached flow diagram for this process ok
Suresh,
Thank you for your reply. Could you please define what you mean by "Ideal Spectrum"? I am assuming "Non-ideal light source" is the spectral power distribution of the illuminant used. What does the product of these two quantities represent (designated by phi in your flow chart.) Lastly, where did you obtain this flow chart or what source material was used to create it?
Did You mean obtaining reaction of the 10 degree observer under D65 to a stimulus given by reaction of 2 degree observer under illuminant C?
I would venture a guess and say no. The two specifications are done with different spectral content and responsivity and it does not sound like you have any spectral information available. However, I would suggest following Aleksei Guzev and calculate the response of relevant materials from their spectral reflectance, using both specifications. Perhaps this will show you some pattern or relation between the two specification that work for the materials you work with.
Regards
Anders
Aleksei,
I have a specification for acceptable color variation mapped as an elipse in x,y,Y color space and the sample material is currently read under illuminant C, 2° observer. I am interested in converting this defined elipse of acceptable color variation to CIE L*a*b* color space. Separately, I want to measure my sample materials under illuminant D65, 10° observer to determine color acceptability. I realize this is a leap to another galaxy and may not be feasible without exhaustive measurements of acceptable colors in the old system and then measuring them under the new conditions and plotting those points in CIE Lab space. I see no easy purely mathematical conversion.
Dr. Thorseth,
My problem is more a matter of mapping my ellipse of specified color variation into a new color space. I don't think I will be able to establish a single delta E specification and will probably have to determine the acceptable variation in L, a, and b separately.
Thank you both for your input.
Felicia
You can find lots of formulae and spreadsheets here:
http://www.brucelindbloom.com/
Best regards,
Christian Greim
You can convert xyY to tristimulus values and use an inverse matrix to gain the original colour signal. Isolate reflectance factor from colour signal, and then use the reflectance and D65 to calculate new tristimulus values through 10degree cmf, and lastly reach new xyY values.
If You have a little skills in programming. Here You can find a very good library for Python: http://colour-science.org/ You can find the libraries them self on GitHub https://github.com/colour-science/colour/tree/develop/colour
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