Canon filed a patent (2012-88427) in Japan for 600mm f/4 and 400mm f/2.8 lenses:
- Patent release date: May 10, 2012
- Patent filed on October 18, 2010
- 600mm f/4 lens:
- Focal length: 585.00mm
- Aperture: 4.12
- Image height: 21.64mm
- Lens length: 468.50mm
- Back focus: 90.78mm
- Lens design: 15 elements in 9 groups, one aspherical element, two UD elements
- 400mm f/2.8 lens:
- Focal length f = 391.86mm
- Aperture: 2.88
- Image height: 21.64mm
- Lens length: 367.51mm
- Back focus: 50.01mm
- Lens design: 14 elements in 9 groups, two aspherical elements, one UD element
