The Hasselblad XPan 90mm f/4 was one of the interchangeable lenses for the XPan, a dual-format panoramic rangefinder camera produced from 1998 in partnership with Fujifilm, which sold the same body and lenses under its own TX-1 and TX-2 names. The 90mm was the longer of the two lenses launched with the original XPan.
The lens couples to the XPan's rangefinder for focusing and covers the camera's panoramic 24x65mm format as well as standard 24x36mm frames when switched to normal mode. It uses the XPan's proprietary bayonet mount, unique to the XPan/TX-1/TX-2 system and shared with no other Hasselblad or Fujifilm line.
As a moderate telephoto on a panoramic rangefinder, the 90mm f/4 suits distant landscape and travel subjects where the wide panoramic frame benefits from a longer field of view than the standard 45mm lens. Rangefinder coupling keeps it compact next to SLR telephotos of similar reach.
XPan lenses hold value in the used market given the system's following among panoramic film photographers, and the 90mm is scarcer than the 45mm. Check the rangefinder coupling focuses accurately, confirm the aperture ring clicks correctly, and inspect the front element for coating wear.