Interview: Q&A with Canon Engineers on the new EOS R Mirrorless Camera

Imaging Resource has published their interview with Canon engineers about the development of the new Canon EOS R ($2,299 at AmazonB&HAdorama) mirrorless system.

Canon EOS R Autofocus – 5,655 points?! Really?

It turns out what’s being referred to are the number of AF point positions you can choose from, when in single-point mode and using the rear-panel arrow keys. When you press one of the arrow keys, the box showing the single AF “point” moves a small step in the chosen direction. Adding up the number of steps in each direction, you’d likely come up with the claimed 5,655 points.

Canon’s unique Dual-Pixel AF technology means that every pixel on the sensor can simultaneously be used for phase-detect focus determination and to create the image. Basically, an AF point could be anywhere on the array.

So, while there’s an entirely separate question of how the camera system manages all of the possible AF-point locations, Canon does have a unique advantage, in that the processor can essentially form an AF point anywhere on the sensor surface, because every pixel in the array (at least anywhere that can “see” light rays coming from both sides of the lens) can be used as a focus pixel if desired, without producing any artifacts in the image.

EOS R AF points are all line-type

As is the case with the new Nikon Z7 and Z6 full-frame mirrorless cameras, the autofocus points in the EOS R are all horizontally-oriented line-type points, meaning they’re sensitive only to subject detail in that direction.

How did they manage 100% vertical AF coverage?

The EOS R’s PDAF points are all line-type horizontal points, so there’s no need to be able to see light rays from the top and bottom of the lens. So it’s no problem having 100% vertical coverage. (Which makes me wonder why the Nikon Z7 doesn’t also have 100% vertical coverage, vs. 90%.)

How does EOS R autofocus compare to cameras like the 5D Mark IV?

So it’s no surprise that the engineers response was a little equivocal, but I think that’s an excellent sign for the EOS R. They said that relative AF performance depended on the subject; that the EOS R would win sometimes and the 5D IV or 1D X II other times. They didn’t elaborate on what subjects they thought each would be best at, but I thought it was significant that it wasn’t all one way, and that the EOS R in fact would win some AF matchups, even against some of Canon’s top SLRs.

How did they end up with the 20mm flange depth? Is that a limitation?

The answer surprised me: It was all about strength and ruggedness. They said that their first consideration in choosing the flange structure was the physical ruggedness of the system, and they felt that 20mm was what they needed to meet their goals for overall strength.

How will the optical quality of the new RF-mount lenses compare with the best EF-mount ones?

They were quick to say that differences are “easily noticeable”; that is not subtle at all. As an example, the current Canon EF 24-70mm f/2.8L II USM is a very well-regarded lens. But when compared to the new RF 28-70mm f/2 optic, they said that the new RF-mount lens is as sharp at f/2 as the 24-70 at f/2.8, and only gets better from there. Also while they didn’t characterize it with respect to a particular lens, they talked a lot about how much having a large element close to the sensor helped when it comes to correcting aberrations.

Some contacts aren’t currently used(!)

They declined to say what sorts of functions they might be intending for the currently unused contacts, and it’s possible that they don’t even have specific plans for some of them yet. But I found it very interesting that they’ve made allowances for future needs this way. (As I’ve now heard multiple times, they want the RF mount to last them the next 30 years.)

4K video specs, why not better?

When I asked the engineers why the limitations in 4K, their reply was a bit cryptic, mentioning the “CMOS sensor system”. A little might have been lost in translation, but I think what it boils down to is that Canon may not yet have the technology to enable full-frame/no-crop 4K readout from their chips.

So, looking across their line, it looks like 4K readout across a full 35mm frame is an issue for them.

As noted, though, the good news is that the EOS R isn’t merely as capable as the 5D IV in doing 4K video, but it has a much improved codec to trim file sizes at the same relative quality as well.

Canon EOS R: $2,299 at AmazonB&HAdorama

Canon EOS R with 24-105mm Lens: $3,399 at AmazonB&HAdorama.

You can read the full interview at Imaging-Resource.