Computer animation (CGI) in its various forms has come to dominate the animation industry. There are even consumer-level animation programs that amateurs can use to create their own animation. More recently, Adobe corporation introduced the CS3 Extended version of its famous Photoshop application. This program allows users to create animation, but there are certain limitations to the process.
No 3D Animation
Unfortunately, although the extended version of Photoshop CS3 does have the ability to import 3D objects and (to a degree) manipulate them, it does not combine this with the ability to actually pose the figures in a scene. Thus, you cannot in Photoshop create the kind of CGI animation based on 3D models that most people have come to expect when they hear "computer animated."
Limited Figure Posing
Even when it comes to simpler 2D figure animation, CS3 lacks any real support for "rigged" figures (of the sort you would see in a program like Aniboom). This means that what you can, with some effort, created grouped figures made up of elements on different layers, each element has to be individually moved to created an overall figures movement. The only alternative to this is to create and sequence "drawings" with each separately drawn to represent the action in a layer. And this is no better than cel drawing.
No Scene Tools
Full-fledged computer animation programs (like Maya or Vue Infinite) have tools and functions designed to help you create the overall scene in which you are placing your animation, such as atmospheric, lighting or terrains tools. Photoshop CS3 has none of this. All this means that while Photoshop CS3 does a good job in creating simple animated graphics, it is no substitute for a real animation program.