Canon Patent Application: Dual teleconvertor telephoto

This patent application is certainly novel.  Taking a page from the Canon 200-400 1.4x telephoto, this telephoto prime (using what seems to be in this patent application to be a rather simplistic design) has the added ability to add not one, but two different teleconverters into the light path.

While this may be far fetched it seems, it should be noted that this gets built in top of a 400 / 5.6 a very reasonable lens and one in which people have been clamoring for replacement.

What is interesting about this, is that one of the teleconverters, is a focal reducer, taking the telephoto down to a 300/4.0, so you basically have three telephoto lenses in one lens body; 300/4, 400/5.6 and a 600/8 mm lens.  This could be a very sweet lens if it makes it into production.

Nominal lens:

focal length 391.89 
F-number 5.80 
view angle 3.16 
Image height 21.64 
total lens length 299.31 
BF 167.00 

With teleconvertor (B)

Focal length 560.02   
F number 8.29   
angle of view 2.21   
image height 21.64   
lens total length 299.31   
BF 46.56 

With Teleconvertor (C)

focal length 286.00   
F-number 4.23   
view angle 4.33   
Image height 21.64   
total lens length 299.30   
BF 110.04   

Japan Patent Application 2019-70689

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