Ok, thanks for very informative asnwers!
I thought up one cheap alternative: if I buy a webcam with good picture, remove the infrared filter and buy one additional IR light. This should me a lot more easyer to install.
I need to lighten up about 5 meters and I also have one usual backyard light, that is always on. Also need a good software for this.
But still, which software to use. I prefer some good one (even shareware).