Canon has applied for two new Diffractive Optics (DO) lens patent. They are the 300mm f/2.8 DO and 400mm f/2.8 DO. My readers know I have owned the EF 400mm f/4 DO IS II since its announcement in 2014 and its predecessor, the Series I lens.
This is an excellent lens for sports and wildlife photography and new DO lenses are rumored to be on next year's Canon's EOS-R camera lineup announcement.
Japan Patent Application 2018-189878
Focal distance: 392.58
F number:2.91
A half field angle: 3.15
Image height: 21.64
Length of the lens: 363.53
BF: 59.15
Focal distance: 293.40
F number: 2.91
a half field angle: 4.22
Image height: 21.64
length of the lens: 274.00
BF: 59.35
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