One of the most popular, if not the most popular “big white lens” is the Canon 300mm f/2.8L IS. We’re still waiting to learn more about an RF version of the lens. It’s our understanding that Canon has done a complete ground-up redesign for the RF 300mm f/2.8L IS USM.
A new patent showing a bunch of super-telephoto optical designs has appeared, and all of these optical formulas come with a built-in 1.4x teleconverter.
We think that a 1.4x built-in teleconverter would be quite welcomed on an RF 300mm f/2.8L IS USM.
Canon RF 300mm f/2.8L IS USM 1.4x
Focal length: 300.00mm
Half angle of view: 4.12°
Image height: 21.64mm
Overall length: 320.00mm
Back Focus: 49.68mm
There are also 400mm, 500mm, 600mm and 800mm optical formulas in this patent.