The
illusion of the motion picture is created by flashing a progressive
succession of static (still) images projected onto the same location
of the screen. Each successive frame is incrementally different
from the preceding frame, creating the illusion of motion. If you
have ever examined a length of film, the increments of movement
between frames will soon become obvious as you compare the slight
differences of the subject's advancing positions. Frames are projected,
one frame at a time, the light from the projector is blocked while
the frames are changing but this is happening at warp speed but
the human eye does not readily notice the screen momentarily going
black (the brain ignores these blanks and confuses itself to see
motion where there is none). If the screen did not go black during
frame changes, the illusion of movement (persistence of vision)
would turn into a psychedelic blur.
