Canon Patent For 400mm Lens With Built-In 1.4x Extender

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