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Preloaded sources

Learn about the sources that come preloaded in the CS Calculator 2.0


The CS Calculator 2.0 comes preloaded with reference sources. These sources include CIE standard illuminants for luminaire and daylight sources, blackbody radiators, and other standard sources such as halogen, metal halide, low pressure sodium, and high pressure sodium.

CIE Standard Illuminants

The International Commission on Illumination, widely known as the CIE (an initialism based on its French name, Commission Internationale de l´Eclairage), promotes the international exchange of information relating to “the science and art of light and lighting, color and vision, photobiology and image technology.” Since the early twentieth century, the CIE has published and continues to update standard illuminants, which are defined spectral power distributions that serve as reference light sources for calculations and specifications for experimental conditions. Illuminants A, B, and C were introduced in 1931 to represent incandescent light, direct sunlight, and average daylight, respectively. The various D Illuminants represent phases of daylight, Illuminant E is the equal-energy illuminant, and the F Illuminants represent fluorescent lamps of various composition. A variety of these standard illuminants are included in the CS Calculator 2.0 for reference.


A blackbody is radiator of electromagnetic energy that is at a uniform temperature whose radiant output in all parts of the spectrum is the maximum obtainable by thermally generated processes when at the same temperature. It is called a blackbody because it would absorb all the radiant energy that falls upon it (and then re-emit it with a spectrum according to its temperature). All other thermal radiators can be classed as non-blackbodies. Non-blackbodies radiate less in some or all wavelength intervals than a blackbody of the same size and the same temperature. Blackbody sources can provide a useful reference for correlated color temperature (CCT).

Custom Sources

If you plan to use an LED source especially, it should be noted that each LED product is unique and can have varying qualities which cause them to have vastly different color qualities, such as color rendering index (CRI) or circadian stimulus (CS), from one to another, even if it is classified as the same CCT. For this reason, it is important to upload the particular source(s) used in your product or lighting design. With the continual replacement of legacy sources with LEDs, some of the pre-loaded sources become obsolete; however, they are still useful for historical purposes or when becoming familiar with the calculator.

Uploading custom sources is encouraged for lighting designs that employ LED products that have vastly different spectral power distributions, even when they share the same CCT. SPD data for custom sources should be obtained from the manufacturer or collected via spectroradiometer in situ. The leftmost SPD data column should be composed of wavelengths entered as integers with a minimum of 1-nm increments. The corresponding power values can be either relative or absolute. In the absence of custom source data, the pre-loaded sources can be useful for general reference and familiarizing oneself with the operation of the calculator.

To learn more about inputting your own custom sources into the CS Calculator 2.0, see Add custom source


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