in our photography class, it is either frame within frame, or
double images. everyone calls it different things, but universally
called frame within frame. :)
If you mean frame within a 'door' frame. then it is called a
sub-frame
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A bed frame is a frame of a bed.
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Frame-by-frame means you do a frame(picture) and then modify it
to make it move. Am I being clear enough?