...Yet the images often have lens flares and diaphragm shadows added to them, so they will look like they were shot with a film camera. I've even seen animated effects like dinosaurs kicking up dirt and mud that sticks and splashes onto the non-existent camera lens that is "photographing" them.

I do this kind of thing for a living, and adding "camera artifacts" is almost a must for some shots (I don't do movies--yet--just still shots.) In fact, Photoshop comes with an effect that automatically generates those lens flares! I also create artificial blurring of large objects across a focal length, and even generate the speckles seen on a close-up of a photograph. These things are barely visible to the naked eye, but somehow people see the difference.

In computer-generated movies, the main thing that has to be added is the blur that movement creates on film. The human eye sees the lack of this as "wrong" in a movie. Other "film" quirks that are often artificially added are camera shake, the overshooting that often happens when a cameraman quickly pans to follow a moving object, and odd artifacts like the weird "reversal" of spinning blades or wheel spokes.

Before computer graphics, one great innovation in stop-motion animation was the invention of "go motion," where an animated creature model was moved by special techniques to create a real film "blur." Obviously, true stop motion has no blur whatsoever.

This was first used in "Dragonslayer," and it added immensely to the realism.

In the computer-animated movie "Monster House," the normal computerized blur technique was eliminated to create the feeling of old-style stop motion.