Originally Posted by ntenny
This is an interesting question. Let's assume that we can utilize this concept & technology without limits, for the time being (e.g., with the product in question, it's limited to F1.2 lenses that will act on APS-C as an F0.9 lens).
There are certain lenses in the large format world for which we have no equivalent in smaller formats, and so people go out of the way to shoot them on LF & film in this day & age. The Kodak Aero-Ektar on 4x5 (or 5x7) comes to mind (my fave, by the way: http://www.flickr.com/search/?q=aero...64%40N00&s=int).
178mm F2.5 lens on 4x5 translates to something like a 53mm f0.8 lens on full frame (ref: http://www.pointsinfocus.com/tools/d...ns-calculator/). We do not have such a lens at our disposal on FF.
IF there can be a reducer like this that can attach to this large format lens and concentrate the light so that it will act like a 53mm f0.8 lens on my Canon 5Dmk2, then EFF YES, I would purchase such an adapter for $600, in a friggin' nanosecond.