In modern cinema, the limits to what can be achieved on screen are limited only by the director's imagination (or, more accurately, their budget). The constraints of special effects have all but been removed as computer technology has advanced to the point where practical effects, prosthetics and traditional compositing techniques have all but been made redundant. That's why James Cameron made Avatar a couple of years ago and not, say, in the eighties. It simply wouldn't be possible. What CGI doesn't account for is the decades of incredible visual effects that have appeared in films before it really got to a point that it didn't look like a crappy video game cut scene. There's plenty of examples of bad, dated special effects out there, but just as many that have held up even today - often using much more ingenious, or else downright insane, methods than simply bunging it into a computer to render for a week. Creatures created using marital aids, actors being put in genuine danger, electrical tape, and the unorthodox use of women's tights all factor into the twenty weird ways classic special effects were made.
Tom Baker is the Comics Editor at WhatCulture! He's heard all the Doctor Who jokes, but not many about Randall and Hopkirk. He also blogs at http://communibearsilostate.wordpress.com/
