With emitted light you work in the additive colour domain, and
reflected light is subtractive colours. See the differences in
RGB (screens) and CMYK (printers), e.g. to see yellow you can
emit R+G, or subtract B. Emitting a colour is easier to control
than subtracting, because reflected light depends on the product
of the (emitting) light source and the material BRDF. BRDF in
General BRDF applied to leaves, where it is interesting how
visible light and NIR light acts differently, which is useful in
agricultural engineering. I used this theory myself to
successfully make an algorithm that can detect scab on apple
leaves. The strength is controllable in both cases, so you can't
see that emitted light is stronger. The perceived strength is a
function of the wattage you burn off from the light source,
distance and spread, and the integral in your viewer sensitivity
spectrum of the light spectrum. This is why LED light seems
stronger for the same amount of wattage as a halogen light. The
halogen does emit more lig