7 February 2010
illuminance = lumens / metre2
the salient difference between illumination and radiance is that illumination considers the power of light in relation to the sensitivity of the human eye at various wavelengths.
brightness on the other hand seems to be illuminance's subjectified sibling - the gauge of which rests tentatively on perceptions shoulders
an ulbricht sphere measures diffused light in manners i don't fully understand
▪▪▪