If two sources, S1 and S2, of light are shining on a ball, and we are given the formula, L1(P) for the amount of light reflecting off the ball at point P caused by light source S1 and into a pixel, 'p' in the image plane of a camera, and similarly L2(P) is the amount of light reflecting off the ball at point P caused by light source S2 and into the same pixel, 'p', on the same image plane of the same camera. Then can we say the total amount of reflected light at point 'P' into pixel 'p' on the image plane is equal to L(P) = L1(P) + L2(P)?

In other words, is there a superposition principle for the intensity of light? It seems that when two lights shine on a surface, the resulting surface is always brighter.

**Edited by Dobob, 7 November 2016 - 03:32 AM.**