OK, I am trying to remember something from my highpower rifle days, but am having a case of CRS. Assume I am shooting a black bullseye using a receiver sight and a post front sight. I am zero'ed for a dull overcast day. What is the effect of the POI with the same sight picture if the sun comes out, shining on the target? Does it make me shoot lower or higher. I remember the adage "light up, sights up" but I cant remember exactly what it means. (really BAD case of CRS!! ) HELP!!