I can not quite understand the question, and answers. Why would the GFX MOUNT not accommodate lenses which would cover 56x40mm sensor?
I agree that the original question is a bit ambiguous, or has perhaps been misinterpreted. I rephrased the subject line to reflect two questions of possible interest:
1) Can the Fujiifilm G mount for the GFX accommodate lenses that cover a larger format like 52x40mm? (the current largest sensor format)
2) Can some or all of the lenses made for the 44x33 format GFX cover these larger formats without problems like vignetting or poor optical correction beyond the 55mm diameter of the image circle of the 44x33mm sensor?
On #1, I am skeptical that the throat is wide enough to avoid vignetting with those larger formats. A rough guideline is that for an idealized perfectly telecentric lens (exit pupil at infinity) the lens mount opening must have a diameter of at least
(sensor diagonal) plus (flange focal distance)/(minimum aperture ratio)
For the G mount, the sensor diagonal is 55mm, the flange focal distance is 26.7mm and the minimum aperture ratio so far is f/2, setting a minimum of about 55mm + 12.4mm = 62.4mm.
If the larger Sony sensor, 54x40mm is used, the diagonal size increases by 12mm to 67mm (and for "645" film format it increases by 15mm to 70mm).
I doubt that the G mount has that extra 12mm of diameter, which would add bulk and weight while adding no value to the 44x33 format. But does anyone have the specs for G mount?
On #2 I have already commented, but to update briefly: the basic optical designs for lenses at long enough focal lengths, say 90mm and up, have a good chance of producing a large enough image circle, but some potential hazards are
- the narrowness of the optical path at the rear of the lens due to a possibly too narrow lens mount diameter,
- design optimization to minimize aberrations over the intended 55mm diameter with the trade-off of poor performance outside that circle, and
- internal rectangular anti-flare baffles which block all light that does not contribute to the intended 44x33mm image.