Just a thought about the lens mount diameter and focal length. In a Tele the light between the mount and film is more or less parallel. E.g. my 300mm Tele shows some vignetting on the F3 viewfinder, as the mirror is a little bit smaller than the film plane. So I guess that for a 300mmf1.0 the mount is not the constraint. The diameter of the diaphragm would be 300mm and the front lens would have a diamter of approx. 400mm. This is slightly bigger than the 300/2 with 183 mm diameter. And the weight would be about 40-50 kg. The 300/2 has 7.1 kg. And it may be slightly expensive, especially the crane which goes as accesoiry. For the shorter lenses the rear element is probably the constraint. All the above is just a guess. Best wishes Thomas Buro
