If you have two clips, A and B, then you overlay A on top of B, and decrease the capacity of A, you can be left with a totally new and interesting shot that no one else would have.
USING DIFFERENT FILTERS EACH TIME THE COUPLE WERE IN A DIFFERENT TIME WAS SOMETHING WE WORRIED ABOUT, WE DIDN'T WANT IT TO GIVE THE AMATEUR EFFECT. BUT USING SUBTLE TINTS TO THE OVERALL IMAGE HELPED DISTINGUISH THE TIME THEY WERE IN.