Question: Can you get color temperature from spectra

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miramon asked on February 01, 2018 18:00
219 | 1 answers | #15659


If I am correct it is a question of making an algorithm. Having wavelength data it should be possible to calculate color temperature from a spectra from a light source like a led. Most professional spectrometers give a result in Kelvin for color temperature... That would be great for me who am using this spectral workbench for a lighting project.

CCT



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See https://spacemath.gsfc.nasa.gov/astrob/5Page55.pdf The lambda max of the spectrum (i.e. maximum wavelength) in nm is plugged into the equation 1,897,000/peak max of spectrum (nm) = Kelvin degrees. So as the maximum wavelength goes from red to blue the temperature of a star at least increases as expected because the blue end is higher in energy (frequency). A place to start?

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1 Answers

Color temperature is the perceived 'color' of light emitted from an ideal black-body radiator due to it's physical temperature in deg-K. An ideal black-body radiator has a uniform broad spectrum; the Sun and incandescent light are reasonable approximations. CFLs and LED have narrow spectral lines so they do not nicely correlate with color temperature. A CFL's 'color temperature' rating is purely a human perceptual approximation of the light color from a broadband source at that temperature.

IF the source has a broad 'black-body' spectrum, then the following approximation may apply. Measure the spectrum and find the approximate 'peak' output wavelength, then use:

Color Temp (deg-K) ~= (2.9 x 106) / (spectral peak(nm))

eg: (2.9 x 106) / (618 nm) ~= 4700K (again, assuming broad-spectrum light)


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