Mathematical description of the relative spectral power distribution of a real or imaginary light source, that is, the relative energy emitted by a source at each wavelength in its emission spectrum.  

The following is a list of standard Illuminants specified by the CIE (Commission Internationale de l'Éclairage) - International Commission Illumination:

• Lighting A - This represents an incandescent light source like a tungsten filament.
• Lighting C - Represents average daylight.
• Lighting D50, D65, D93- The D-series illuminants represent different times of the day in an outdoor setting. D50 is a standard for Graphic Arts Industry. As the number increases from 50-93 the light gets more bluish (i.e. more bluish component is present).
• Lighting: F1, F2, F3, F4, F5, F6, F7, F8, F9, F10, F11, F12 - These are the fluorescent light simulators.
  • F2, F7, or F11 Illuminants - These illuminants simulate most indoor lighting.
  • F2 - Represents a typically cool white fluorescent source.
  • F7 - Represents a broad band daylight fluorescent source. Examples of F7 are GE and Philips daylight fluorescent sources.

Note: D50 is the default setting for the Graphic Arts Industry.

Generally, if you know the type of lighting and the brand of the bulb you use to view the print, you can obtain the information from the manufacturer about the CIE standard illuminant they are simulating (http://www.cie.co.at/cie/). Then you can use that illuminant to build the profile. If the print will be viewed outdoors, then using either D50 or D65 is appropriate.

See ICC Build Options.