How to plot the Plankian Locus alongside SDs on CIE chromaticity diagram plots?

[ThomasWilshaw]

Hi,

Apolgies if I am missing something obvious but when plotting SDs on the chromaticity chart (e.g. colour.plotting.plot_sds_in_chromaticity_diagram_CIE1931()) is there a way to also show the Plankian locus on the same chart? Likewise is there a simple way to mix and match SDs, XYZ coordinates, primaries etc. all on one chart?

Thanks

[KelSolaar]

Hi @ThomasWilshaw,

Two ways:

import colour

colour.plotting.plot_sds_in_chromaticity_diagram_CIE1931(
    [colour.SDS_ILLUMINANTS["D65"]],
    chromaticity_diagram_callable_CIE1931=lambda **kwargs: colour.plotting.plot_planckian_locus_in_chromaticity_diagram_CIE1931(
        [], **kwargs
    ),
)

figure, axes = colour.plotting.plot_sds_in_chromaticity_diagram_CIE1931(
    [colour.SDS_ILLUMINANTS["D65"]],
    show=False,
)
colour.plotting.temperature.plot_planckian_locus(axes=axes)

Cheers,

Thomas

[ThomasWilshaw]

Thank you that worked perfectly

[ThomasWilshaw]

Out of curiosity why are the colour temperatures on the planckian locus plotted as lines rather than points?

[KelSolaar]

Those are Iso Temperature lines where points on the line have the same colour temperature but not the same $D_{uv}$. We then talk about correlated colour temperature.

[ThomasWilshaw]

Thank you :)