I watched this fascinating movie again recently and was curious to know more about the conception. A lot of info available on the net. Some highlights:
“It’s inconceivable now for people to think how we actually did the CG,” Lisberger said. “There was no movement. Computers could only generate individual frames. There was no way to digitally put them on film so you actually set up a motion picture camera in front of a computer screen and you filmed it frame by frame. Some of the frames took hours to generate.” (from a 2017 interview with Tron’s director Lisberger and Jeff Bridges).
For you hardware buffs, here is a rundown on some of the hardware used to create the images in TRON. MAGI operates with a Perkin Elmer System 3240 computer to make the calculations for each picture it generates. The system functions with two megabytes of MOS memory and two 80-megabyte disk drives, and talks to a Celco DFR 4000 computer, which is used to generate the pictures onto a monitor.
“ (from a 1982 Starlog article about CG in Tron)
“The live-action scenes inside the computer world were filmed in black-and-white on a black set, then printed on large format Kodalith high-contrast film and hand-colored with photographic and rotoscopic techniques to give them a “technological” appearance. Those multiple layers, printed on large format and painted, required an even greater workload than the traditional cel animation.” (from a good article about the conception.)