A patent application showing an unusual f/2 zoom from Canon has appeared in Japan (Patent application: 2018-132675). It's possible that this zoom lens is related to a mirrorless camera body with its short BF distance.
Canon News tells us that the patent itself deals with a floating focus system to help reduce the size of the lens.
Japan patent application 2018-132675:
Focal distance 90.00 125.01 145.99 109.96 130.49
F number 2.06 2.06 2.06 2.06 2.06
a half field angle 13.52 9.82 8.43 11.13 9.41
Image height 21.64 21.64 21.64 21.64 21.64
Whole length 242.35 242.35 242.35 242.35 242.35
BF 16.70 1 6.70 16.70 16.70 16.70
Focal distance 72.03 115.04 145.99 92.39 123.70
F number 2.06 2.06 2.06 2.06 2.06
a half field angle 16.72 10.65 8.43 13.18 9.92
Image height 21.64 21.64 21.64 21.64 21.64
Whole length 217.72 217.72 217.72 217.72 217.72
BF 22.47 2 2.47 22.47 22.47 22.47
Focal distance 72.00 114.84 146.00 92.60 123.41
F number 2.06 2.06 2.06 2.06 2.06
a half field angle 16.72 10.67 8.43 13.15 9.94
Image height 21.64 21.64 21.64 21.64 21.64
Whole length 210.32 210.32 210.32 210.32 210.32
BF 21.80 21.80 21.80 21.80 21.80
The optical formulas show a very short zoom range, but being an f/2 lens, that would make some sense.
Optical formulas in the application:
- 90-130mm f/2
- 70-125mm f/2
- 70-125mm f/2 (shorter backfocus)
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