The H2f was primarily designed for Hasselblad's CF backs. It was also designed to close the H platform. It does not work with Phase, Leaf, or Sinar backs. I don't know too many people that ever shot film with it. It was also compatible with the HC28mm lens, the HTS adapter, and eventually the 35-90 zoom. It was basically an H3D. The H4X will accept other backs. But you can only get one if you trade up from an H2F.