Attached are a couple of quick tests using an older E-EF speedbooster (not ultra as that bigger). Nearly fits without OLPF housing removed. (of course you have to be very careful here) - Just wanted to see if there would be enough room to fashion a dumb EF lens mount to this, will have to 3D print one. Shots are 'Whacked' so no mount and a bit of tilt and shift distortions to be assumed.
Going by tests from Full Frame 35mm (Sony A7s) 5k now matches Full Frame 35mm. 6k is porthole of course. A 35mm at 4k is about a 50mm on full frame (single picture).
Sometimes I really want higher frame rates at without so much crop, and extra speed is a nice touch.
Custom OLPF (not shown) is tacked onto the front glass of the speedbooster although this has some IR cut I used a IR cut filter (52mm) on this Nikon 35mm Lens.
To do. Create a housing for the speed booster modded version of OLPF option so we don't loose OLPF and IR cut. Create a lens mount to accommodate the new flange distance.
Of course I would love metabones to do this, even if a custom low order amount was placed.