Canon Patent Application: Canon RF 17-70mm F4-5.6 BR
We first discovered Canon desigining a 17-70mm Full frame lens a while ago, and here is another patent application discussing such a lens.
however, this lens has a twist, as it contains a BR element (a rather large one as the element closest to the sensor is the BR element).
It isn't all good though, the lens requires image stretching basically most of the way from 17mm to at least 28mm, even though it's only slight at 28mm. The inclusion of the BR element allows Canon some additional freedom to make this lens quite small, at a size of 80mm at its shortest length.
A lens like this could be the "bridge" lens that Canon is thinking about when coming out with an APS-C camera body. This would be an okay lens on a crop camera (still bigger than your normal kit lenses though) and an excellent walkaround lens on a full-frame camera.
Canon RF 17-70mm F4-5.6 BR
Focal length 17.50 28.00 58.00
F value 4.10 4.50 5.70
angle of view (°) 51.50 38.16 20.77
Maximum image height 22.00 22.00 22.00
Real image height 19.47 20.98 21.94
Total length 108.50 114.27 158.50
BF 21.38 33.45 49.01
Japan Patent Application 2021-182053
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