Canon has been working on their own focal length reducers. Lens adapters commonly sold under “speedbooster” or similar names, these adapters translate a larger projection circle, like that from a full frame lens, to the smaller sizes needed by APS-C and smaller sensors.
Such “speedboosters” (and the reason they got their name) is that they come with the benefit of effectively increasing the maximum aperture. They’re the polar opposite of a teleconverter, which gives a longer focal length equivalent while reducing the light entering your lens.
Below are some of the focal length reduction formulas mentioned in the patent.
Specification and lens arrangement of master lens 1 (18-55mm, F2.8)
- Zoom ratio: 3.05
- Focal length: 17.50 – 53.3 mm
- F number: 2.80 – 2.80
- Half angle of view: 36.65 – 13.71
- Image height: 13.02 – 13.02mm
- Lens length: 148.81 – 172.70mm
- Back focus: 35.51 – 40.31mm
Specification and lens arrangement of master lens 1 with reducer 1
- Focal length: 11.36mm
- F number: 1.82
- Half angle of view: 36.67
- Image height: 8.46mm
- Lens length: 142.26mm
- Back focus: 2.00mm
Specification and lens arrangement of master lens 2 (34mm, F1.4)
- Focal length: 34.20mm
- F number: 1.45
- Half angle of view: 32.32
- Image height: 21.64mm
- Lens length: 129.16mm
- Back focus: 39.35mm
Specification and lens arrangement of master lens 2 with reducer 5
- Focal length: 23.92mm
- F number: 1.02
- Half angle of view: 32.33
- Image height: 15.14mm
- Lens length: 125.59mm
- Back focus: 2.00mm
While these types of converters are more likely to appear for the EOS M series, CR suggests that some of these designs may be intended for a future APS-C EOS R body.
I’m not sure I see the sense in Canon making an APS-C version of the EOS R. Assuming they really aren’t giving up on the EOS M line, I think an RF mount lens EF-M body adapter would make much more sense.
Although Canon has covered a lot of focal length reduction designs with these patents, we’re yet to see any exist in a real product. So, exactly what features Canon might include with these adapters, or if they’ll even release any of them at all, only time will tell.
What lens adapters do you want to see come to reality?
[via Canon Rumors]