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The C version is in a Synchro Compur shutter. The CF version in a Prontor CF shutter.
The design of the barel has changed.
The lens barrel of C lenses has knurled metal rings, the CF barrel has a rubberized focussing ring.
Aperture and shutterspeed rings are coupled by default in C-lenses. You have to press a tab to be able to set a different aperture-shutterspeed combination.
The rings are not-coupled by default in CF lenses. You can move them together by pressing a button.
The C-lenses have both X and M flash synchronisation settings, the CF only X.
The C-lenses have a selftimer too, the CF-lenses do not.
The front mount is different too: the C-version of the 50 mm Distagon has a series 63 filter mount, which takes unthreaded filters, which are held in place by a threaded retaining ring, or ditto lens shade.
The CF lens has a bayonet 60 mount for both filters and lens shades.
The "F" in CF indicates that the leaf shutter can be disabled, so that only the diaphragm works. This makes using these lenses on "f"ocal plane shutter Hasselblads a bit easier.
The optical design of the C and CF version 50 mm Distagon is the same. However, the CF 50 mm Distagon was at some time replaced by a CF FLE 50 mm Distagon, the FLE standing for floating lens elements.
The FLE version allows adjusting the spacing between lens elements (it has a second, 'zone'-focussing ring to do that), to maintain quality throughout the entire focussing range. Or rather improve quality in close up photography.