Rather defeats the object, to

Rather defeats the object, to be honest. A few people attach specialist lenses – as in extremely long ones, or ‘special’ ones, but DSLR lenses usually lose you the very features ⅔ B4 cameras excel at. Zooms that stay pin focus and can go in/out fast or very slowly – the reporting back to the camera for auto iris and other things. Most cameras with the adaptor can take whatever lenses you have available, but you also get a change of field of view too, as the sensors are different sizes, so the usual result is a zoom in – with some loss of quality. A DSLR wide angle looks pretty standard on a B4 mount.