Canon is working on their own “speedbooster” style adapter to use EF lenses on M bodies

December 10, 2018 by John Aldred 3 Comments

Lens adapters to put Canon EF mount lenses onto M mount bodies are nothing new. Canon’s had one for a while now. But when it comes to speedbooster style adapters, one company’s pretty much had the market sewn up, and that’s Metabones. But Metabones only produces such adapters for Sony, Micro Four Thirds and Fuji crop cameras. At least for now.

A new Japanese patent (2018185393) suggests that Canon will be working on their own, now, though, breathing some new life to their EOS M mount line of cameras – as well as their EF mount lenses as they make the push towards full frame mirrorless.

Speedbooster lens adapters work in a slightly different way to regular lens adapters. They still allow you to mount one type of lens onto a different type of camera, but they also contain optics which effectively shrink the size of a lens’s projection circle. This shrinking of the projection increases the field of view that the sensor sees, and it intensifies the lens’s light output – in a similar way that moving a projector closer to a wall reduces its projection size and increases brightness.

For all intents and purposes, speedboosters reverse the crop factor of a smaller sensor. Not all speedboosters are created equally, however. Some offer wide 0.58x magnification, while others only offer a reduction of 0.71x. So, your field of view will be different depending on the adapter you use.

The Canon patent shows a 0.8x reduction, which brings that 1.6x APS-C crop factor to about 1.28x. So, it’s not quite going to give you a full frame field of view, being more like Canon’s older 1.3x APS-H crop factor, but it would still definitely be wider than when using a native lens of the same focal length on an EOS M camera without the adapter.

This isn’t the first EF to EOS M speed booster style adapter. Viltrox makes one with a 0.71x reduction for a mere $156. But, chances are, Canon making their own, with obvious access to all their own intellectual property means they can probably make one that’s faster and more reliable. Even if the field of view isn’t stretched quite as much as one might like.

There’s no word from Canon on whether or not this patent will actually come to market in the form of a real product. But given Canon’s four EF to RF mount adapters launched with the Canon EOS R, we wouldn’t be surprised if they did. Lens adapters have become far more accepted than they have been in the past, and it will mean that Canon won’t need to duplicate as many lenses for three completely different mounts.

You can find out more about Patent 2018185393 here, but you’ll have to hit the search, they don’t allow direct linking.

[Canon News via DPReview]

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Jaedyn Chilton

I think there is a mistake in the title, as an adapter is not needed to adapt EF-M lenses to EOS M bodies
- Kaouthia
  
  Oops! Thanks, Jaedyn. Fixed. :)
Stefanie Daniella

FYI:
A RECENT Canon Japan Patent 2018-189864 is nothing like typical Metabones Speedboosters.

Metabones speedbooster focal-reducer generally allows a larger Lens Image Circle to be concentrated down to an image circle half the original FF area, approximately 0.7071x magnification (or half the area, with brighter intensity by 1 stop) That’s it. Nothing more.

However, Canon’s patent addresses also reducing EXCESS “peripheral” light that often is different (undesirably darker) than ideally at the center, especially for already very fast wide aperture lenses.

The patent design employs a Lens Converter with several VFC (Variable Flare Cutters) which can take on same shape as the Master Lens projection rear opening (can be circular, oval, rectangular, or any other shape). This design is larger mechanically, so, it’s meant for larger lens systems, like RF system itself (built-in), or as an interchangeable modular converter lens; but NOT meant for smaller EFS nor built-in to EFM lenses.

Since different lenses of different focal lengths have different rear projection opening sizes, the VFC Lens Converter’s Variable Flare Cutters (VFC) is designed to be optimal in selecting the ideal opening sizes of various VFCs, more than 1, physically positioned in various locations in between optical elements, in the lens converter, chooses whether to use a VFC# closer to Master Lens or a VFC# farther from the Master Lens, depends on the FL of Master Lens, and aperture size of Master Lens chosen by the user.

Such a Multi-VFC Lens Converter can effectively REDUCE unwanted peripheral light that degrades the overall optical UNIFORMITY, so there is minimal light falloff at the widest brightest apertures of the Master Lens, and can detect + identify what kind of Master Lens is being used, in order to select optimal VFC sizes and shapes, while additionally offering some Focal Reduction, such as reducing larger image circle to a smaller image circle.

This is IDEAL for EOS R (NOT EOS M) so any FF Lens, say an EF/TSE Lens would use an interchangeable Converter version; whilst any particular upcoming RF Lenses could have such VFC Converter Lens BUILT-IN, instead!

The EOS R system is also ideally suited to use higher-rez FF sensors, so “milder” crops, with larger 0.7071x focus-reducers could be used, where various multi-aspect ratio sub-FF sensor areas can be used, instead of just smaller APSC 1.6 sensor area.

Imagine, say, a 63.45mp EOS RS (3.69um pixel size) with Fast RF Zooms with built-in 0.7071x Focal-Reducers (with Multi-VFCs)! It could have various multi-aspect S35 Sensor ratios with up to 30.66mm image circle, with 3:2, 4:3, 16:9, dci, 2.35:1 modes, having “crop” resolutions ranging from 24.4mp to 32.9mp!

The patent example happens to show only a basic 0.79 Magnification, which is okay for only FF 43.2735 mm down to 27.32mm (small APSC 1.6 only) … however …
…
This can easily be scaled further upsized to include handling Canon FF Lenses with image circle sizes beyond minimum “nominal” 44mm of EF/RF lenses, up to 55mm on EF Lenses, and as high as 67.2mm, like on TSE Lenses.

So, future RF Lenses can easily have 55mm image circle as do several EF Lenses already have.
The patent specifies a 0.80 value, which is ideal for EF with 55mm image circle to be reduced to 44mm exactly, and with VFC employed, any undesirable peripheral light falloff can be reduced via pre-programmable VFCs.