Canon Patent Application: Internal Zoom RF-S F4.0 lenses

This is a curious patent from Canon. These are without a doubt higher-end lenses and are certainly for APS-C. Canon specifically mentions that these types of lenses would be advantageous for video as the center of gravity doesn't change.

Fixed-length zoom lenses are known in which the overall length of the lens does not change during zooming. Such a zoom lens is suitable for video shooting and the like because the center of gravity does not change much during zooming. In recent years, zoom lenses have been required to have high zoom magnification and high optical performance over the entire zoom range for video applications.

But the image circles described in these embodiments are all APS-C and not Super-35 (super-35 has a slightly larger sensor size) but Canon isn't doing APS-C video seriously. So right off the bat, I'm sort of looking at this patent application as something that would be very unlikely to happen.

What's even curious is that if these lenses are for video (as Canon is describing) I would think that image stretching isn't something Canon necessarily wants to do in the video pipeline but these lenses do require it on the wide end.

We can dream of some L-grade quality zooms for APS-C even if Canon is thinking of them just for video, can't we?

Canon RF-S 20-120mm F4.0

                      Wide     Middle      Tele
Focal Length         20.02      50.03    119.95
FNO                   4.08       4.08      4.08
Half angle of view   34.40      15.16      6.31
Real image height    12.33      13.66     13.66
Total length        165.00     165.00    165.00
BF                   13.54      13.54     13.54

Canon RF-S 20-135mm F4.0

                      Wide     Middle      Tele
focal length         20.01      50.01    134.95
FNO                   4.08       4.08      4.08
Half angle of view   34.29      15.08      5.61
Real image height    12.33      13.66     13.66
Total length        168.51     168.47    168.50
BF                   13.82      13.82     13.82

Canon RF-S 18-100mm F4.0

                      Wide     Middle      Tele
Focal Length         18.41      50.02    101.96
FNO                   4.08       4.08      4.08
Half angle of view   36.59      15.05      7.42 
Real image height    12.33      13.66     13.66
Total length        146.50     146.48    146.49
BF                   13.77      13.77     13.77

As with all patent applications, these may never transpire into an actual patent or product, but it's a glance into the research happening inside of Canon.

Source: Japan Patent Office 2023-182926

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