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DescriptionI checked that color coordinates (xy) are correct, but XYZ values are 1.0685 times less than expected. standard condition (CIE 1931 2deg observer, E illuminant) Code for ReproductionNo response Exception MessageNo response Environment Information===============================================================================
* *
* Interpreter : *
* python : 3.10.2 (tags/v3.10.2:a58ebcc, Jan 17 2022, 14:12:15) [MSC *
* v.1929 64 bit (AMD64)] *
* *
* colour-science.org : *
* colour : 0.3.16 *
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* Runtime : *
* imageio : 2.14.1 *
* matplotlib : 3.5.1 *
* numpy : 1.22.1 *
* pandas : 1.4.0 *
* scipy : 1.7.3 *
* six : 1.16.0 *
* *
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Out[70]:
defaultdict(collections.OrderedDict,
{'Interpreter': OrderedDict([('python',
'3.10.2 (tags/v3.10.2:a58ebcc, Jan 17 2022, 14:12:15) [MSC v.1929 64 bit (AMD64)]')]),
'colour-science.org': OrderedDict([('colour', '0.3.16')]),
'Runtime': OrderedDict([('imageio', '2.14.1'),
('matplotlib', '3.5.1'),
('numpy', '1.22.1'),
('pandas', '1.4.0'),
('scipy', '1.7.3'),
('six', '1.16.0')])}) |
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Replies: 9 comments 1 reply
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Hi @leklbk, I'm fairly confident at this point that our computations whether they are using integration or ASTM E308 are correct. Would you have more details on your conversion? e.g. the spectral distribution you are trying to convert. Cheers, Thomas |
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@KelSolaar Hey, Thank you for the quick response! [ 3.80000000e+02, 9.00000000e-02], I used this SD and expected XYZ values is (17.9243, 18.2737, 17.4361) I also confirmed my calculation shows the same results with measurement data. xy coordinates between these two are identical (0.3342, 0.3407) Thank you for your quick response! |
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Hi, Thanks for the details, this is an interesting spectral distribution! How are your CMFS tabulated? I tried many variants of the integration and I'm certainly finding Y ~= 17. Cheers, Thomas |
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Thank you for your confirmation.
I used this one. Thanks! |
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Thx, we are using the same CMFs and I'm highly confident that our computations are correct, it could be the normalisation. What is your |
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Thanks for your confirmation! I'm not sure what the k value is. |
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I'm not sure how you are performing your computations but at the very basics, this is how it should be done (and it is what we do):
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Thank you for your clarification. I've never considered k for this calculation. Maybe that's because I've been working in the display field.
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Looking at your spectral distribution and seeing how non-uniform it is, I was actually wondering if it was the radiance of an emission source. If you set k
Normalisation constant :math:`k`. For reflecting or transmitting object
colours, :math:`k` is chosen so that :math:`Y = 100` for objects for
which the spectral reflectance factor :math:`R(\\lambda)` of the object
colour or the spectral transmittance factor :math:`\\tau(\\lambda)` of
the object is equal to unity for all wavelengths. For self-luminous
objects and illuminants, the constants :math:`k` is usually chosen on
the grounds of convenience. If, however, in the CIE 1931 standard
colorimetric system, the :math:`Y` value is required to be numerically
equal to the absolute value of a photometric quantity, the constant,
:math:`k`, must be put equal to the numerical value of :math:`K_m`, the
maximum spectral luminous efficacy (which is equal to
683 :math:`lm\\cdot W^{-1}`) and :math:`\\Phi_\\lambda(\\lambda)` must
be the spectral concentration of the radiometric quantity corresponding
to the photometric quantity required. |
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Thanks for your confirmation. that's clear to me. |
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Thank you for your clarification.
I've never considered k for this calculation. Maybe that's because I've been working in the display field.
Now not sure I have to do this,
Thanks!