As with lenses, it is not possible to change flashguns to work on different manufacturers cameras.
Nikon D200, D2X, D2H, D2Hs, D70, D70s, and D50 will function in “i-TTL” mode. D100, D1X, D1H and D1 will work in D-TTL mode.
Illumination angle of Sigma flashguns is adjusted to 35mm film format. Therefore when using these flashguns with APS-C size digital SLR cameras, the illumination angle will be wider.