An optical formula patent application for an 8-15mm fisheye zoom lens has appeared at the USPTO.
The patent covers both the APS-C (EF-M) and full-frame (RF) mirrorless mounts as the backfocus for each embodiment is well shorter than the EF’s 44mm.
Focal length: 5.30mm – 9.51mm
F-number: 3.50 3.50
Angle of view: 181.00° 182.00°
Image height: 7.50mm 13.50mm
Total lens length: 77.28mm – 69.52mm
BF: 11.09mm 16.77mm
Focal length: 8.01mm 15.30mm
F-number: 3.78 4.60
Angle of view: 177.30° – 183.10°
Image height: 11.15mm 21.64mm
Total lens length: 105.23mm – 103.57mm
BF: 12.00mm 28.46mm