Does Units and Scale matter? (m, cm, mm)

[ivanebeoulve]

I always work in meters, in the blender unit settings, I made a sort of test showing the same scene, a red cube illuminated by a sun lamp and a sky texture, changing only the units settings under the scene tab: from m, to cm, and mm.

what I expected was a change in the color bleeding, as I understand it, light intensity decreases logarithmically with distance, so a bigger scene should have different GI calculations than a similar but with different units scene, I guess what I'm wondering is if the change of this setting in blender makes a diference to the v-ray algorithm.

my test shows that there IS a diference but tbh the results are not as intuitive as a thought they would be. a "smaller" cube has a decrease in exposure. (using a physical camera with the same settings) that gives no change in the color bleeding

1. what causes this change in exposure? and is it normal?
2. to properly follow a linear workflow, where GI calculations are correct, does it matter what units I work with?

[andybot_cg]

Maybe if you had something like fog in refraction or sss I would think the result would be different, but afaik the light bounces from an infinite source will be the same regardless of scale. As far as the physical camera, I guess that just follows real world scale - i.e. you'll need more exposure for a macro image.