Canon Patent Application: Canon RF 28-70mm F2.8L Dual AF motors

This design will never find itself in an actual lens but the design may lead to the 24-70mm F2.8L II.

This design has dual focus motors, most likely would be dual focus motors, which Canon has not employed in their normal zoom.  Canon does, however, use dual autofocus motors in their RF 70-200mm F2.8L.

The embodiments themselves aren't really worth talking much about - they are either really poor full-frame image coverage or 28-70mm - neither of which would ever get an "L" grade normal lens these days.  The dual motors do however lead to a rather compact lens, as shown by this embodiment being only 129mm at its widest lens (it's a reverse zoom) and 96mm at its shortest.  The RF 24-70mm F2.8L is 135mm to 160mm as a comparison.

focal length       28.84  39.89  67.90  
F number            2.91   2.91   2.91  
Half angle of view 32.65  28.06  17.67  
Image height       21.64  21.64  21.64  
total lens length 133.18 115.94 149.46  
BF                 13.48  19.38  27.78  

Japan Patent Application 2021-179550