The reflection of any specular materials must be 0.95 to 0.99.
Formula:
Light_destination (to darker) = light_sources * reflection ^ maxdepth
light_destination and light_sources in W/m^2 (eg: sun 1400 W/m^2)
^ - it's power (mathematics)
Therefore, I have adviced you the very big number of "maxdepth" (100 (reflection 0.95) and 500 (reflec 0.99) or more) due to the real life.
