Lesson 4 Lecture & Discussion
The Moving Image

Lessons 2 and 3 should have given you a good understanding of the basic technology of motion pictures. Now we’re going to look a little more philosophically at what filmmakers actually do with the technology at their disposal.

This lesson covers the three most important facts about movies:

  1. That motion pictures work at all depends on a defect in human vision.
  2. What you see can be contiguous or non-contiguous. In other words, a filmmaker can choose to simply let the camera roll (mise-en-scène) or to carefully splice shots together one after the other in sequence (montage).
  3. Unlike any other visual art, because it exists in time as well as space, film has the ability to change point of view while you are watching it. This ability comes from the unique tool of the moving camera.

Fooling Your Eye: Persistence of Vision

Persistence of vision allows our brains to create motion pictures from a series of still images shown in rapid succession. (Do you recognize this shot? You will soon!)

It is important to realize at the outset that movies depend on a trick. It is only because your retina retains an image for a certain amount of time that we can perceive pictures that move when we watch the projection of 18, 24, 30, or more still pictures per second. This phenomenon is called persistence of vision. As anyone who has ever seen a strip of film knows, there’s obviously no movement there: the illusion of motion comes when these still pictures are projected fast enough so that the viewer can’t separate them psychologically.

No other art depends on this kind of illusion. Technically, any recorded sound presents itself to the ear exactly like a real sound. When we look at a photo or a painting, what we see is what we get: there is no perceptual trickery there. (How you interpret a painting or a photograph often depends on cultural codes you’ve learned, but that is a different level of significance.) Only motion pictures require this perceptual deception. We see motion where it simply doesn’t exist.

The motion-picture camera takes a picture, the shutter closes the lens, the film is moved to the next frame, the shutter opens, another picture is taken, and the process begins again. (There may be no physical film in a video camera but the operation is much the same.) When you watch a film, the same process works in reverse.

What’s more, when you are looking at a movie projected in a theater, for a large part of the time (almost 50 percent), the screen you are watching is blank—totally dark. This is the time when the shutter is in front of the projected image while the next frame is pulled into place for projection. (When you are watching a film on a video screen, this "dark time" is replaced by a slowly fading image of the last frame that was projected. Not quite as much of a cheat, but close.)

Ingmar Bergman used to have nightmares about this conundrum: his art was based on deception! He suffered guilt pangs.

The bottom line is that motion pictures simply do not exist in reality—not even in the most advanced digital systems. They are all an illusion based on a defect in the physiology of human vision. The only place they exist is in our minds. In fact, the title of this lesson―The Moving Image―is a truism and, at the same time, a misnomer.

If they don’t exist, how come they have had so much power over us for the last hundred years? Perhaps simply because of that deception! All arts depend, for their characteristic effects, on the limitations of their respective media. Movies are no different. If there were a way to record reality without depending on persistence of vision, cinema wouldn’t be what it is today: a creative tension between the scene (mise-en-scène) and the editing of a scene (montage).