The use of so-called alternative glass on Canon EOS bodies has been popular for some time, and sometimes the reasons are compelling and the reward is great. However there are also people experimenting with medium format lenses on Canon EOS cameras via an adapter, perhaps in the hope of achieving something closer to medium format levels of detail. Unfortunately this is not the case. Medium format lenses resolve more detail overall mainly because they have a much larger image circle and use much larger pieces of film, or larger digital sensors. However, the amount of detail resolved per millimeter may even be less than a good 35mm format lens.

Using medium format lenses on a Canon makes little sense to me for the following reasons:

– medium format lenses are generally larger and heavier than the 35mm format equivalents of the same focal length
– medium format lenses are generally slower (smaller maximum apertures)
– medium format lenses are generally more expensive
– you will generally lose functionality such as AF, EXIF, auto-aperture, etc

There are two notable exceptions. It makes sense if:

– you already own the medium format lenses, or
– you need the extra image circle because you are using a tilt/shift style adapter