CIE Standard illuminant D65 is intended to represent normal 'noon' daylight illumination in the environment.
Its relative spectral power distribution is that of a filtered tungsten halogen light source at a temperature of approximately 6500 K.
Illuminant D65 should be used in all colorimetric calculations requiring representative outdoor daylight,
unless there are specific reasons for using a different spectral power distribution.
CIE Standard illuminant D65 is intended to represent normal 'noon' daylight illumination in the environment. Its relative spectral power distribution is that of a filtered tungsten halogen light source at a temperature of approximately 6500 K.
Illuminant D65 should be used in all colorimetric calculations requiring representative outdoor daylight, unless there are specific reasons for using a different spectral power distribution.
It's the illuminant used in the RGB color space.