Egami has discovered a new patent filed by Canon. The patent describes a 400mm f/2.8 fixed focal length lens with built-in 1.4x extender.
The lens in the patent features a built-in extender of 1.4x, just like the one found in the EF 200-400mm f/4L IS USM lens. The lens EF 400mm f/2.8 described in the patent will offer a focal length of 560mm and a maximum aperture of f/2.8.
See the patent details as follows translated by Machine.
Canon Patent For 400mm Lens With Built-In 1.4x Extender
EF 200-400mm f/4L IS USM lens with a built-in 1.4x extender
Description and self-interpretation of the patent literature
- Patent Publication No. 2014-115410
- Publication date 2014.6.26
- Filing date 2012.12.7
- Master lens
- Focal length f = 390.09mm
- Fno. 2.90
- Half angle ω = 2.01 °
- Image height Y = 13.66mm
- The overall length of the lens 367.66mm
- BF 44.00mm
- 15 pieces of 11-group lens configuration
- Two fluorite
- Example 1
- Focal length f =-226.69mm
- 1.41x magnification
- Five 4-group lens configuration
- One piece of one sided aspherical
via EG
