in blenderdoc,there are sait that with area light,size parameter don’t affect energy amount,but whith a value of 1 my scene are surexposed and with a value of 100 energy is very low,someone can explain me?
Looks like what is happening is that the lamp’s energy is being spread out over the area. So your size 100 area lamp only has 0.01 energy coming from each square unit (but still adds up to 1.00 energy). The area lamp projects light in a single direction, so spreading out the light means less light will fall on your model, so it looks much darker.
I expect the document writer was being very precise: the lamp’s energy (a separate setting) wasn’t affected by changing the size of the area. But it sure does make a huge difference in the appearance of the render. It was probably a design decision, it could just as easily have been coded to make the energy setting affect the energy for each square unit, which would have increased the total energy as the lamp got larger.
thanck for explanation but i don’t understand very well
If you change the Size value of an Area Lamp (type in the value next to Size) the energy value remains the same. If you Scale the same lamp with S the Energy value (typed) stays the same but the display brightens if you scale it bigger and dims if you scale it smaller.