A film fan from childhood, Ralston was already experimenting with 8mm film and camera techniques while a teenager. He put together a forty minute audition film that landed him work at Cascade Productions where he worked in various capacities from prop builder to stop-motion photographer (including a stint working on commercials that featured the Pillsbury Doughboy). In the 1970s, at the urging of Dennis Muren, Ralston joined Industrial Light & Magic as a camera assistant on "Star Wars", and by 1980 was optical effects photographer on "The Empire Strikes Back". He showed an affinity for outer space, creating the visuals for three "Star Trek" films ("The Wrath of Khan", 1982; "The Search for Spock", 1984; and "The Voyage Home", 1986), as well as "The Return of the Jedi" (1983).
But Ralston's work here on earth has been equally impressive. His interactive cartoons in "Who Framed Roger Rabbit" (1988), his comic zombies in "Death Becomes Her" (1992) and his high-tech wizardry in "Forrest Gump" and "The Mask" (both 1994) won awards and raves from critics and audiences alike. Among his less spectacularly visual films have been "Cocoon" (1985), the second and third installments of "Back to the Future" (1989 and 1990) and "The American President" (1995). He is also responsible for the computer-generated animals in the jungle fantasy "Jumanji" (1995), starring Robin Williams. Ralston left Industrial Light and Magic in late 1995 to assume the presidency of Sony Pictures Imageworks.
Ralston was one of the subjects profiled in "A Night of Movie Magic" on the Discovery Channel (1995). Ralston's first TV venture in special effects was the "You, Murderer" episode of HBO's "Tales From the Crypt" (1995) which utilized techniques perfected in "Forrest Gump" to make Humphrey Bogart an active participant in a new story line.