Canon Patent Application: Cheap ultra-wide prime lenses for FF and APS-C

This is an odd patent application (2024-006604), let's dive into the dirty details. These embodiments are odd for several reasons.

The 18mm image height lenses would have to have an extreme amount of image stretching for full frame. The usual image height for full frame lenses is atypically 21.64mm in Canon's patent literature. So even with a perfect lens sharp down into the corners, you are talking a 17% loss of resolution across the entire image. There is one lens that I think would be the best fit for a cheap full-frame lens, and that is two embodiments of the 15mm F4.5, but even with that, an excessive amount of stretching is necessary to fill the frame. However, if this lens is cheap, it may still be a good value.

The crop lens 10mm F3.5 doesn't seem as bad, as it's an 11.72mm image height down from Canon's traditional 13.66mm, but it's still a 14% across-the-board loss of resolution on a perfect lens, and sitting with a back focus distance of 10mm with a large rear element also seems like there's too many compromises to be a lens that makes it into production.

These lenses would have to be very low cost, otherwise, the lenses shown in the embodiments are would simply be a thought experiment. A little different than what I normally do, is that I'm going to bold the numbers I think are problematic.

Canon 15mm F4.5

Focal length            15.45
F number                 4.60
Half angle of view (°)  49.36
Image height            18.00
Lens total length      115.26
BF                      13.50

Canon Crop 10mm F3.5

Focal length             9.97 
F number                 3.50 
Half angle of view (°)  49.63 
Image height            11.72 
Lens total length       72.73 
BF                      10.06

Canon 16mm F4.5

Focal length             16.00 
F number                  4.60  
Half angle of view (°)   48.58 
Image height             18.14 
Lens total length        99.94 
BF                       13.04

Canon RF 15mm F4.5

Focal length             15.53 
F number                  4.60 
Half angle of view (°)   49.20 
Image height             18.00 
Lens total length       120.00 
BF                       15.70

Canon RF 15mm F4.5

Focal length             15.60 
F number                  4.54 
Half angle of view (°)   49.09 
Image height             18.00 
Lens total length       120.00 
BF                       18.33

Don't get me wrong, I love the fact that Canon is exploring cheaper ultra wides and even super ultra wides. And there's the possibility that we may see the 15mm come out for the RF mount. But like all the patent applications I talk about, this is just a look into Canon's research.

Japan Patent Application 2024-006604

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