There is a scene when Superman is in his evil phase and sitting at a Bar. He is looking at himself in a mirror, and uses his heat vission to melt the mirror. Yet in Superman II, Superman used a truck's side view mirror to reflect Zod's heat vision, causing lots of damage.
When Superman is flying to the Grand Canyon, there is a very dirty lense mark.
Lot's of visable wires in the factory fire scene.