Originally posted by Viking42 If an old folder has a 45mm lens then it would be a 135 film camera. As far as I know there was never a wide angle 120 folder. Most or all of the latter had either 75 or 80mm lenses if 6x6, or 105mm if 6x9 (=45mm in 135). I'm pretty sure Zeiss made both 135 and 120 format Ikontas, although I think the 135 ones are pretty rare and the most common Ikontas are medium format. Great cameras, BTW, and capable of excellent images if you get a good one with a Tessar lens.
I think all of the wide angle optical designs back in the day would have needed to extend back too far to fit into the body of a medium format folder while still allowing it to, well, fold...
But I'll admit, I always thought the focal length of the lenses on fixed-lens rangefinders was a design optimization between the desired focal length, desired aperture, the sophistication of the lens design, the compactness of the camera body, and any other bits of ergonomic or technical weirdness (where's the shutter go?).
So a complex, fast, wide angle lens wasn't going to be on a super compact camera, for example, but you might see a simpler, slower design...
My Argus C4 has a 35mm f4.5 Lithagon that's not tiny...
-Eric