My friend purchased Nikon F-100 camera recently, but without any other Nikon stuff (except one 50mm f1.8 AF lens) so far. Then he checked user's manual, and red that using of non-Nikon flashes may damega the camera! Is it for real, or just a marketing (OK, you purchased Nikon camera, now you have to purchase Nikon flashes, etc)? Any practical advise? My personal opinion is that he may put any manual flash combined with manual aperture and shutter camera settings, but... that's damn expensive camera!