To add an example, I'm building an optical system. I use DV camcorders,and the models I've recently bought run about $350 each new. I believe the OptiTrack cameras are in the same price ballpark. You need at least 2 cameras to do 3D, and 3 cameras to use Dr. Svoboda's camera calibration software. You can write the image processing routines in Java (free) on your computer (not free - uusally). So, there's hope someone will develop a really cheap setup, and in fact, there's one in the Renderosity Marketplace store, but it doesn't do automatic marker recognition. That means that you have to hand identify every marker in every frame. I own the software, and will use it for small pick up work, but it's too tedious for longer animations. Cheers, Michael