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

Last updated: May 6, 2025 3:28 am

Published: November 18, 2016

1 Min Read

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We didn't think the built in extender on the EF 200-400mm f/4L IS 1.4x was going to be a one off. Now a patent showing an optical formula for a new EF 400mm f/2.8L IS with a 2 stage built in extender has appeared. This would give the lens a focal range of 400mm, 560mm & 680mm.

Patent Publication No. 2016-191761 (Google Translated)

Published 2016.11.10
Filing date 2015.3.31
Focal length 392.57
F-number 2.90
Angle of view 3.15
Image height 21.64
Overall length of the lens 371.15
BF 44.00
The first state magnification 1.40
The second state magnification 1.70

We had heard previously that an extender was being tested in a new 800mm lens, but this may make more sense.

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ByCraig Blair

Craig is the founder and editorial director for Canon Rumors. He has been writing about all things Canon for more than 17 years. When he's not writing, you can find him shooting professional basketball and travelling the world looking for the next wildlife adventure. The Canon EOS R1 is his camera of choice.