Jonny Engelsvoll, who can only be described as the best kind of camera geek, just combined a Fujinon XA55x9,5 ENG lens with a Panasonic GH4 to see what would happen. Basically, the Fujinon is designed for use with ENG/EFP cameras, the kind of thing you see at sporting events. The lens is designed to cover 2/3″ sensors, but with a 2x extender, Engelsvoll was actually able to get the lens to work… surprisingly well.
With that 2x extender, the lens/camera combo becomes a 19-1050mm f/1:3,4. That crop factor gives the same AOV as you would get out of a 44-2415mm lens on a full frame camera. Holy smokes!
In Engelsvoll’s own words, “It worked surprisingly well.”