Kenko/Tokina displayed a new T-mount 400mm F/8 mirror lens at the 2012 international CES that looks very interesting! The aperture is pretty slow but this helps the lens to be very compact and from looking at photos of the lens attached to a camera it looks small even by mirror lens standards and could possibly be the smallest 400mm lens I've ever seen! Having a T-mount this lens will be adaptable to just about any camera you can think of but will it deliver anywhere like decent IQ?
It seems a lot of people relying on google translate have come to the incorrect conclusion that the T-mount to Micro 43 and T-mount to NEX adapters were the big story when obviously the lens is the big deal! Likewise the $200-250 price estimate applies to the lens and not just the adapter! There is no current release date although it looks like they are aiming to have it on the market some time this year.
I'm very interested by this lens so hopefully it will perform quite well optically but I wont get my hopes up, there are some great mirror lenses out there but not many!
Photo from DC.Watch