The 'standard' focal length on almost any traditional folding 6x9 camera is 105mm. So a 180mm lens would be a medium verging on long telephoto equivalent if you accept the 105mm standard lens analogy. So for instance a 90mm (Angulon perhaps) would therefore be a slightly wider than standard lens, perhaps (off the top of my head) a 40mm equivalent in 35mm terms.

Steve