These links will download a tutorial for making a conceptual design of a camera. You may have already seen a video about it in the first webcast of AutoCAD 2010.
I'm now giving access to the dwg file and a pdf with the explanation of the whole process.
I hope it's useful.
This is the final result that you should get in a couple of steps, as already seen on videos!
Remember that the dwg file is 2010 format, so you need to have AutoCAD 2010 in order to open it.