What is a Signal Generator, and when would you need one for Video?

Why on earth would anyone need a signal generator (also called a function generator) for video?

Comparing Camera Systems for Feature films

Thinking of buying a camera for your next low-budget independent feature film? Below is a comparison chart of five systems to help you decide. The cameras are the Sony PMW-F3, the Panasonic AF100, the Canon 600D, the Canon 5D Mark II, and the old and outdated JVC GY-HD111E. Click on the image to enlarge: