I have played around with this a little, using the camera pi module gives good results, but means you must mount the pi close to the camera. I wanted to use USB

I have played around with this a little, using the camera pi module gives good results, but means you must mount the pi close to the camera. I wanted to use USB cameras but the USB bus on the pi is too slow. From a single USB webcam I was getting around 15fps. The newer pi's may have a faster USB bus.