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I see it is possible to purchase many different color temperatures in light bulbs from 3500K (in the red spectrum) to 6500K (in blue spectrum) all the way to 10,000K and even 20,000K or higher.

All bulbs available for purchase however comes in specific ranges. For example, you will not find a bulb that produces light in 5400 Kelvin or exactly 5200 Kelvin and so on. In other words, while there are many ranges available they are still limited to certain numbers.

My question is - how is the color temperature determined? In other words, does a given material always produce the same color temperature? Or is it possible to tweak a substance to produce any color desired? If yes, how would this be done?

FYI, I am interested in producing specific temperatures for a scientific experiment.

Thanks

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  • \$\begingroup\$ Use a tungsten or led and the apropriate filter like this leefilters.com/lighting/colour-details.html \$\endgroup\$
    – GR Tech
    Apr 15 '15 at 5:11
  • \$\begingroup\$ for the origin of 'colour temperature' look at en.wikipedia.org/wiki/Stefan%E2%80%93Boltzmann_law . Rather than use colour temperature (used mainly by photographers for 'white balance') for a scientific experiment it is much easier to specify the source in terms of wavelength(s). These can then be related to colour temperature if necessary. Be careful to differentiate between full and line spectra sources (e.g. between thermal (filament) bulbs and gas discharge tubes) \$\endgroup\$ Apr 15 '15 at 11:18
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For commercial lamps, including incandescent bulbs, the reported color temperature is (or at least should be) a correlated color temperature. So it might not even have the same color coordinates as black body radiation of any temperature. When running on alternating current (AC), the filament of an incandescent bulb cycles its temperature so its effective spectrum is an average over close-to-black-body emission spectra at different temperatures. Running the bulb on direct current (DC) instead of AC may get a bit closer to black body radiation. You can lower the voltage or current to get a lower filament temperature. Tungsten melts at 3695 K.

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