The 300mm Hasselblad lens is outstanding for sharpness and reach. Also excellent with the 1.7 extender which equates to 510mm on a medium format camera. Also excellent with two 1.7 extenders attached for a total of 867mm on a medium format camera. Who else has this but Hasselblad?
Ummm...Mamiya/Phase One, and Pentax 645D, both exceed this. One (or two) 2x teleconverters on their 300mm lenses reach further than one (or two) 1.7x teleconverters on Hasselblad's 300mm.
Sure, the Mamiya and Pentax 2x converters are not autofocus, but
neither is the 1.7x when used on on the Hasselblad 300mm lens.
Furthermore, the Mamiya 645 has 500mm lenses (three: f4.5, f5.6, f8) and the Pentax 645 has a 600mm f5.6; these can all take teleconverters as well. Hasselblad H doesn't have anything longer than 300mm; not without the expense of the CF adapter, and then the aperture is only f8 for the 500mm CF lens and f5.6 for the 350mm CF.
Not trying to start a war; nothing against Hasselblad; delighted you are winning contests; but you did ask the question, and I had to answer it!
I've seen one reference to a Zeiss Tele-Tessar 1000mm f8 for Hasselblad V. Anyone know anything about it? Leaf shutter, or for the focal plane shutter bodies? I know the Rollei SL66 (focal-plane shutter) line offered it as well.
Ray