Introvision Technology Outland

Outland was the first film to use the Introvision front projection process

Outland was the first motion picture to use the Introvision process (Wikipedia), a variation on front projection that represented a significant leap in practical visual effects.

Standard front projection composited actors against a flat background plate

To understand Introvision, you first need to understand standard front projection:

  1. A projector sits to the side of the camera at a 90-degree angle
  2. A half-silvered (beam-splitter) mirror is placed at 45 degrees in front of the camera
  3. The projector beams an image onto the mirror, which reflects it toward a Scotchlite screen behind the actors
  4. The camera, looking through the mirror, sees the actors composited against the projected background
  5. The key trick: Scotchlite is a retroreflective material that returns light almost exclusively back to its source. So the background image bounces brightly back to the camera, but the light falling on the actors (who are not retroreflective) is too dim to register (Wikipedia)

This gives you actors against a background plate — but everything is flat and two-dimensional. Actors can only stand in front of the projected image.

Introvision added a second screen and black masks to create three-layer depth

Introvision's innovation was adding a second screen behind the half-silvered mirror, facing the projector, with black masks cut into specific shapes placed on that rear screen — and matching negative masks positioned in front of the camera (Cinefex #4, via Graham Edwards).

This meant the projected plate could now include foreground elements — objects that appeared to be in front of the actors. Actors moved behind physical black masks held in precise register with matching images projected onto the rear screen, creating the illusion of a live person walking inside a flat plate — behind pillars, under arches, through doorways that existed only in the plate photography (Cinefex #4, via Graham Edwards).

The system could combine three layers simultaneously in-camera:

  1. Background (projected behind actors)
  2. Mid-ground (live actors on set)
  3. Foreground (projected elements that occluded the actors)

The director could see the finished composite in the viewfinder on set

  • Real-time compositing: The director could see the finished composite through the viewfinder on set, unlike bluescreen which required waiting for optical lab work
  • No bluescreen artifacts: No matte lines, color spill, or fringing that plagued bluescreen work of the era
  • Interactive lighting: Because everything was composed in-camera, lighting interactions between elements were more natural
  • Cost-effective: Reduced expensive post-production optical work

Actors had to pantomime and the camera could not track through the plate

  • Actors had to pantomime interactions with objects that weren't physically present
  • The system required extremely precise alignment of all optical elements
  • Scotchlite screens had a limited viewing angle for retroreflection, restricting camera movement
  • The background had to remain static (no camera tracking through the projected environment)

A former stage magician and a USC student built it in the early 1970s

Introvision was developed by John Eppolito — a former stage magician and ABC radio producer — in collaboration with USC film student Les Robley during the early 1970s, later commercialized through Introvision International Inc. (Wikipedia).

Digital compositing made the process obsolete within a decade

Despite its promise, Introvision had a limited career in feature films. Don Shay assessed it in Cinefex:

"Clever" but "too slow and cumbersome for widespread feature film use" — "one of the last innovations of the chemical/optical age." — Don Shay, Cinefex #4 (1981)

After Outland, it was used on a handful of other productions including The Fugitive (1993) and Army of Darkness (1992), but the rise of digital compositing in the 1990s made the process obsolete.

Outland remains the process's showcase — the film where it was used most ambitiously and to greatest effect.

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