Aug 24, 2023

Canon's Latest Lens Patent is One of the Weirdest Designs We've Ever Seen

Canon has filed a patent in Japan that shows what appears to be a compact built-in teleconverter that relies upon external controls and internal actuators to provide photographers with quick access to various focal lengths.

As first reported by Asobinet and later by Canon Rumors, the patent application shows what looks like a fast portrait prime lens with internal teleconverter optics that can be moved in and out of the optical path using external controls.

In a machine translation of the patent, the application describes an optical design that solves the issue of excessively large teleconverters. The patent also describes a system that includes a second lens group “configured to change a focal length range of an optical system to a second focal length range,” which is a roundabout way to describe a teleconverter, which is an optical group that extends the focal length of a lens in exchange for a slower maximum aperture.

However, while typical teleconverters are external components the user attaches manually between a lens and the camera, Canon’s internal teleconverter solution includes inner tubes, cams, and actuators that move an internal optical group into the optical path. Notably, the patent also shows that when not in use, the optical group can be moved entirely outside the optical path without creating a large lens barrel.

Internal conversion optics have been used before, including somewhat frequently by Nikon. For example, the Nikon AF-S 180-400mm f/4E TC 1.4 FL ED VR telephoto zoom lens for F-mount DSLR cameras includes a built-in 1.4x teleconverter enabled with an external switch on the lens barrel. Nikon has employed similar optical technology with a pair of its Nikkor Z super-telephoto lenses, the Nikkor Z 400mm f/2.8 TC VR S and Nikkor Z 600mm f/4 TC VR S.

However, while those lenses with built-in teleconverters are very long telephoto lenses, Canon’s patent application is notable in that it shows diagrams of a much smaller, shorter lens. Canon Rumors notes that Canon’s diagram shows what looks like a 50mm f/1.2-style prime lens and speculates that perhaps the patent could apply to a “possible 50mm and 85mm hybrid lens using a built-in teleconverter, so consider as an example a 50mm f/1.2 and an 85mm f/2.0 built into the same lens and able to switch between the two primes with just a touch of a button.”

That exciting theory corresponds to the lens’s look in the patent application. Canon Rumors also created a nice animation of different figures from the patent application.

It would also make for an interesting lens. A significant benefit of prime lenses is that they allow for faster apertures than zoom lenses, all else equal. However, the cost of using a prime lens, such as a 50mm f/1.2 or an 85mm f/1.4, is that the photographer compromises on versatility.

A teleconverter is one means for changing the focal length of a compatible lens, but attaching and detaching the teleconverter each time someone wants to change framing is tedious and no faster than just swapping in a new prime lens. An internal teleconverter would undoubtedly make the process much faster. Such an internal teleconverter design could also enable a quasi-zoom lens with fast apertures, similar in spirit to something like the Tamron 35-150mm f/2-2.8 lens, albeit in a smaller and lighter form.

In the case of Nikon’s TC-equipped lenses, a large, noticeable hump is created by the space required to put the teleconverter optical group when it is not in use. Canon’s patent poses an alternative to this design and promises a smooth barrel.

Fitting these movable optics inside a lens without creating a large barrel requires an exact and clever optical design. As is always the case with patent applications, the described technology may never be implemented in an actual product. Nonetheless, it is a fascinating idea and one of the strangest patents seen recently.

Image credits: Canon patent application

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