It all began innocently enough, with toys. As far back as the 1830s, people played with such things as the phenakistoscope. This was a revolving disk with drawn figures arranged around the center. Folks also amused themselves with the zoetrope. This let them view figures on the inside of a revolving cylinder through slits in its circumference. As late as the 1960s, toy makers supplied similar mirrored cylinders. They made these to sit atop revolving phonograph records. Some record makers of the time printed the labels on their “45s” with cartoon characters in various phases of motion. What you saw when you looked into the revolving mirrored surface was what your great-grandparents saw in their zoetropes: figures that seemed to move. The first “motion pictures” were thus actually animations.
mile Reynaud of France took the process a step further when he projected sequences of drawn pictures onto a screen with his Praxinoscope. This applied revolving mirrors and an oil-lamp “magic lantern” to a zoetrope-like drum.

In 1877, Eadweard Muybridge built the bridge between motion pictures and photography. First, he used a series of rapidly shot sequential photographs to analyze the motion of a horse at full gallop. By 1880, however, he found himself reconstructing the motion by fastening his photos to a drum, enlarging and projecting them using the Zopraxiscope, an adaptation of the zoetrope. Voil, moving photographs are born.

And finally, though many debate who is actually responsible for putting all this great thinking together into one device, Thomas Edison is credited with the invention of the modern motion picture projector.

Why do these inventions work? Psychologists and neurologists have isolated two phenomena which they say make us see moving figures instead of a series of stills. They call the first “persistence of vision,” a label for the fact that a response of retina and brain to an image lasts a split second longer than its stimulus. Thus, we see a slide on a screen for a brief moment after someone turns off the projector. If the projector comes on again before the previous image has faded from our retinas, we’ll never have seen the black screen while the projector was off–the picture appears to have been on screen the whole time. If any light or image flickers faster than the decay time of our persistence of vision, we see it as a continuous light or image. Psychologists call the speed at which this happens the “flicker-fusion frequency” of our eyes and brains. As it turns out, most of us will see the flicker in anything flickering slower than 16 times per second.

One of the founders of Gestalt psychology, Max Wertheimer, isolated the second phenomenon and called it “phi,” or visual closure. This is the tendency our brains have of “filling in” the in-between spaces of adjacent visual stimuli. For example: place two lights near each other in a dark room. Turn the first on, then turn it off while turning the other on. When the distance between the lights and the speed of the alternation are just right, you’ll see one light moving from position A to position B rather than two lights. You’ll see something moving across your field of vision that doesn’t exist. When we make a video, we place two very similar pictures one after another in quick succession. An object appears in the center of the first frame and slightly to the right in the second. As viewers, we perceive the object moving to the right; our brain has filled in all the object’s “in-between” positions. That’s phi.

When you boil it all down, videomakers deal in sleight of hand, trickery, illusion. We make ourselves see things that don’t exist. We stare with fascination at a screen that is actually blank a good part of the time; we see things moving across it that really stand stock still in their frames. If a Martian with a higher flicker fusion frequency than ours visited a movie theater, would he be appalled? He’d see a room full of people staring at a long succession of similar still images interspersed with blank screens.

You could see the main character in Ingmar Bergman’s The Magician as a metaphor for the film director or videomaker. He enchants and tries to get people to believe in his magical powers, but he’s only a trickster. It’s really all done with mirrors.

One final thought for the mix. In most of the higher animals, sensing motion is a survival function. Animals use it for discovering when they are under attack and for judging when to attack. So, we videomakers work with a medium made to subvert and trick a mechanism that could be crucial to our own survival. Does its trickery refine our senses of continuity and motion or degrade them?

Stephen Muratore is Videomaker Editor in Chief.


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