Most cameras are C-mount (1"-32t / 17.53mm flange distance). Some are CS-mount (1"-32t / 12.53mm flange distance) and can be converted to C-mount by adding a 5mm spacer. Earlier professional cameras came with an ENG mount (bayonet / 48mm flange distance). Lately, many of the more sophisticated cameras have the option of C-mount or F-mount (Nikon bayonet / 46.5mm flange distance).

Some of the large format lenses now use the SLR thread mount (M42.0 x 1.0) and T thread mount (M42 x 0.75), or even the latest M72 x 0.75t mounting. The M72 can be converted to a smaller thread by means of commercial step-up rings. (www.photofilter.com)

Most lenses are still C-mount. An F-mount lens, with its long flange distance, can be converted to C-mount with the addition of a simple "F to C" converter found in many camera shops. What can't be done is to "stretch out" a short flange distance C-mount lens to a longer flange distance F-mount.

A number of new high performance lenses are being produced with the basic T-mount. Because it has the longest flange distance (55mm), it permits usage of the standard T to C, F, or SLR thread converters.