Canon Patent Application: Supertelephotos

Because of the nature of Canon's extenders, usually, it's impossible to tell if a super-telephoto design was intended for DSLR's or mirrorless cameras.  Some designs we have seen were most definitely mirrorless, with the backfocus exceedingly shorter than that possible for DSLR's - however now that we know that the extenders ingress into the lens, those designs have little hope of becoming reality.  The backfocus of a super telephoto has to be at least 38mm (the sensor to the lens mount distance 22mm ) + ~16mm (the distance the converters ingress into the lens itself).  For a DSLR design, the backfocus has to be at least 44mm + 10-15mm for the convertor.

This patent application contains the full suite of super telephotos including the F200/2.0 which usually never shows up in these applications.  The F200 F2.0 gives us a clue about the intention of this application since the backfocus of the 200mm F2.0 is 38mm.  Because of this, we can assume that at least the F200 and possibly the application itself was done with the intention of the EOS R system.

Canon's goal with this patent application is;

The present invention is lightweight, and aberrations such as chromatic aberration and has an object to provide a well-corrected optical system and an image pickup apparatus having the same.

The embodiments are shown below.

Canon 600mm F4.0

Focal length        585.00
F number              4.12
Half angle of view    2.12
Image height         21.64
Lens total length   475.00 
BF                  103.93

Canon 400mm F2.8

Focal length        392.57
F number              2.90
Half angle            3.15
Image height         21.64
Lens total length   371.15
BF                   75.00

Canon 500mm F4.0

focal length        489.05
F-number              4.12
Half angle of view    2.53
Image height         21.64
Lens overall length 411.08
BF                  100.00

Canon 800mm F5.6

focal length        777.00
F-number              5.80
half angle            1.59
Image height         21.64
total lens length   498.01
BF                  158.67

Canon 300mm F2.8

Focal length        292.53
F number              2.90
Half angle of view    4.23
Image height         21.64
Lens overall length 273.92
BF                   76.35

Canon RF 200mm F2.0

focal length        200.00
F number              2.06
Half angle            6.17
Image height         21.64
Lens total length   196.01
BF                   38.50

Japan Patent Application 2021-039379