What does the "Clamp Direct" and Indirect values mean? I may seem silly but i'm really new to blender. Could you please tell me what are they useful for? Thanks!
$\begingroup$ Here is the plasmasolution's video about the feature: youtu.be/EfB9zj78wW4?t=31s. You can find a brief explanation also in the manual: docs.blender.org/manual/en/dev/render/cycles/settings/scene/… $\endgroup$– CarloNov 8, 2017 at 18:19
Clamp puts a limit to the intensity of light bounced directly and indirectly by surfaces. It can be used to prevent the annoyoing "fireflies" (random intense pixels in your render) but it is advised to avoid using this feature as it harms the realism of the rendered scene.
It is a good advice to never ever use clamping on direct, and if you're going to use indirect, keep the value rather high (close to the clipping value of the view transform you use) so you don't lose too much energy in your render and bounces and reflections stay realistic.
Using such conservative values for clamping will reduce its efficiency at preventing fireflies, but keep in mind that if you're aiming to photorealism clamping should be your last resort.