Personally, given the quality of Hasselblad V, H, and X system lenses, I would want such a focal length reducer to be made by Hasselblad and matched properly to their lens series by the optical and mechanical engineers who have the most information about their lenses. And lucky lucky!!—Hasselblad has just announced a 0.8x 'speed booster' for H system lenses to be used on on X system bodies ... the
XH Converter 0.8.
Of course, this is not directly applicable to V system lenses. There is a V system lens to H system body adapter, but there's no information to imply that you could use that adapter stacked onto this adapter and come up with a seamless working kit. Never mind the cost ... the two adapters together would a ~$3000 expenditure.
Hasselblad chose to go the simple route in the XV Adapter and rely upon the sensor's eshutter for exposure timing already, presumably because they found either the problems of timing the mechanical system for all the wide variety of V system lenses to the X system electronics too complex, not enough of a win, too inconsistent, or just plain too expensive (even for Hasselblad!) to undertake. Or maybe they're still working on it. Regardless, the simple XV Adapter used with the 907x or X1D bodies actually works pretty nicely, assuming you can work around typical eshutter issues.
Of course, another possible way to go, since the 907x/CFVII 50c is a modular system, would be to design a 0.7-0.8x converter that mounts on a V-system 500 series SLR body and uses that in conjunction with the CFVII 50c back and the square crop function. Then you'd have a fully mechanical system between body and lens that works with the already proven electro-mechanical integration of the existing digital back. You wouldn't get any more functionality out of such an adapter mounted onto an X system body, and the fact that most users who have a bunch of V system lenses they want to use almost certainly have a V system body or two to work with already. This makes the most sense to me and avoids all the complexity and source off issues in a V to X focal length reducer (and a good bit of the cost...).
My own tactic for the present, rather than buy focal length reducer, is to just mount one shorter focal length lens on my 500CM when I'm using the CFVII 50c or 907x with the XV Adapter to accommodate the smaller sensor format. A 45-50mm lens on the CFVII 50c back is virtually the same FoV as an 80 on 56x56, a 80mm lens is about the same as a 115mm, a 120mm is about the same as a 170mm, a 150mm is about the same as a 210mm. I bought the XCD21 to give me the SWC FoV, and if I find I want an intermediate wide the XCD 30mm is there too. I don't get the "speed boost" effect this way, but I can't say that I've found that to be a lack.
It'll be interesting to see what does come up in the marketplace, and by whom. I suspect it's all based on how big an audience there might be for these things, how much profit would be available to fund the development and production ramp costs...
G
