If anyone has both the uv vis spectra and colorimetric data (CIE 1931 values) for onme or a couple of coloured samples and could share the data please could you post / send to me?
I need uv/vis at 5nm increment minimum.
I wish to test my software to see if values agree.
Happy to do that except that it will be 380-5-780nm (ie no UV as not needed for colorimetry) and would you like the calculations for CIE 2 degree and/or 10 degree observer and Standard Illuminants A and/or D65? (I also have B, C and easily available.
Hi Stephen,
That would be most useful thank you, apologies for the slow reply as I have been away from the office over the holiday period.
I would like to do calculations for 2 degree at the moment, standard illuminants and D65 if possible :-)
I am just starting my work in colorimetry and have not performed any calculations for 10 degree observer or more recent standards.
Many thanks
Matthew
Attached document. The spectral reflectance values used are the calibration values of two of our reference BCRA tiles, red and green. I have also been able to add the calculations given by NPL.
The reference values xbar, ybar, zbar and illuminants are the extracted values from the 1nm step data (ie the value is that in the 1nm step table). For a sample with narrow peaks and troughs you may get slightly different answers if you average, ie the value at a wavelength is the average of the 5 of which it is the centre wavelength. Probably only D65 will change significantly, being a distribution with peaks and troughs. Arguably the latter is the more correct way to go.
Sorry about empty posting, still getting used to ResearchGate.
Hi Stephen,
That is most useful thank you - I shall work on this and compare myself and get back to you.
Thanks again
Matthew
Hi again,
I have just tested my values and believe I am close but not yet close enough.
Attempting to calculate with D65 illuminant I do have some variation as you anticipated - I get the following:
x=0.633263
y=0.326363
I then attempted with standard illuminant A, and also obtained the same values, suggesting I am doing something wrong. I shall have a look again at my calculations.
Apologies for the multiple posts, that's excellent thank you! :-)
I now obtain (with Std Illuminant A and red):
x=0.666072
y=0.323049
The others seem to agree closely also!
Kind regards
Hello Matthew,
i would like to know whether you are applying this on images or only on data could you please suggest me, actually i am working with images to get mixed portion of colors in an image. so please give me an idea how you are doing ok thank you.
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