I understand the primary difference between the two being that in the former, the light rays at a point is regularly reflected while in the latter, each point throws of light in all directions.
But since the principle of least time must hold, any single point on the screen can reflect light coming from a fixed point in one direction only, right? So I imagine diffuse reflector to be made of super-small mirrors, and these are angled in every which way, spanning all directions in very close vicinities so that at a small point (not strictly the geometric sized point), macroscopically, the light falling is reflected everywhere. But is this thinking correct? And if it is, does it not mean that there is a certain resolution of diffuse reflectors/screens?
PS: Is the specularity solely a property of microscopic regularity or is it something to do with materials too?