Patent : Canon EF 400mm f/2.8L IS USM Lens with Built-in 1.4x and 1.7x Extender

Canon has filed a new patent in Japan. From the application its the EF 400mm f/2.8L IS USM lens with built-in 1.4x and 1.7x extender.

We can see that this new telephoto zoom lens patent shows off 2 stage built in extender (1.4x and 1.7x). So the focal length can be extended to 400mm, 560mm & 680mm.

The current Canon EF 200-400mm f/4L IS USM lens ($10,999 at Amazon, B&H, Adorama) with a built-in 1.4x extender. It can convert the focal range and maximum aperture to 280-560mm f/5.6.

Patent : Canon EF 400mm f/2.8L IS USM Lens with Built-in 1.4x and 1.7x Extender

Take a look at the patent details below translated by Google.

• Patent publication number 2016-191761
  • Release date 2016.11.10
  • Application date 2015.3.31
• Main lens
  • Focal distance 392.57
  • F number 2.90
  • Field of View 3.15
  • Image height 21.64
  • Lens total length 371.15
  • BF 44.00
• Example 1
  • First state magnification 1.40
  • Second state magnification 1.70

via: Egami