Here's an interesting wide angle prime optical formula patent from Canon. It's a non-fisheye EF 10mm f/2.8 for full frame sensors.
Patent Publication No. 2015-102620 (Google Translated)
- Published 2015.6.4
- Filing date 2013.11.22
- Focal length f = 10.30mm
- Fno. 2.88
- Half angle of view ω = 64.54 °
- Image height 21.64mm
- Lens length 124.58mm
- BF 38.00mm
I'm not sure if this would have been part of the EF 11-24mm f/4L development, or if we might actually see a 10mm f/2.8L prime one day. A replacement for the current EF 14mm f/2.8L II?