Hello i’m writing a plugin that will handle ies files in Blender.
After some digging in the source i found this.
/* Intensity values in IES files are specified in candela (lumen/sr), a photometric quantity.
- Cycles expects radiometric quantities, though, which requires a conversion.
- However, the Luminous efficacy (ratio of lumens per Watt) depends on the spectral distribution
- of the light source since lumens take human perception into account.
- Since this spectral distribution is not known from the IES file, a typical one must be
- assumed. The D65 standard illuminant has a Luminous efficacy of 177.83, which is used here to
- convert to Watt/sr. A more advanced approach would be to add a Blackbody Temperature input to
- the node and numerically integrate the Luminous efficacy from the resulting spectral
- distribution. Also, the Watt/sr value must be multiplied by 4*pi to get the Watt value that
- Cycles expects for lamp strength. Therefore, the conversion here uses 4*pi/177.83 as a Candela
- to Watt factor.
*/
Now my question. @lukasstockner97
Since the ies texture seems to take in account the efficacy and ballastfactor etc.
is it correct that one should use a Power value of 1Watt in Blender in order to get correct luminance from the light ?
regards
u3dreal