That's what a Canon patent application seems to suggest, a 300mm f/2.3 mirror lens. Read…
A Canon patent application referring to 200-500mm f/4 and 300-800mm f/8 for full frame sensors, although it is not clear if the lenses for the RF or EF mount.
Canon patent application 2022-26392 (Japan) discusses optical formulas for 200-500mm f/4 and 300-800mm f/8 lenses.
PROBLEM TO BE SOLVED: To provide a zoom lens which has a long focal length and a large aperture ratio, yet has both small size and light weight and high image quality.
Conventionally, a zoom lens has been proposed in which a lens group having a positive refractive power is arranged on the most object side to realize a long focal length and a large diameter ratio (see Patent Documents 1 to 3).
However, a zoom lens having a long focal length at the telephoto end and a small F-number has a large front lens diameter and increases the weight. The zoom lenses of Patent Documents 1 to 3 are insufficient in weight reduction. It is effective to reduce the number of lens components in order to reduce the weight, but if the number of lens components is reduced, it becomes difficult to achieve high image quality.
An object of the present invention is to provide a zoom lens having a long focal length and a large aperture ratio, yet having both small size and light weight and high image quality.