DCWatch posted some information about an internal Canon presentation.
The benefits and advantages of the large diameter of the RF mount featured on the Canon EOS R are discussed. The main reason is that the RF mount allows for a new and improved lens design.
Apparently, Canon had a try to use the EF M mount for their EOS R full frame mirrorless camera (machine translated text):
Initially, Canon also considered to realize a 35mm full size with the EF-M mount of the APS – C mirrorless “EOS M” series, but satisfactory results were not obtained, such as no performance aimed at .And since the system becomes large when unnecessarily increasing the mount diameter, we actually designed multiple lenses, decided to 54mm while looking at the balance of optical merit and size, the strength of the camera and so on.
This didn’t work out well, as it seems.
Canon sees these main advantages of the larger mount:
more flexibility on where the optical elements have to go
larger elements can be placed closer to the sensor
lenses are easier to design
complex lenses like the RF 50mm f/1.2L and 24-70mm f/2L are feasible
vignetting and other optical issues are better controlled
Note that while most of the above points would have been technically done also with the EF M mount, Canon clearly decided to go for the new mount type on the Canon EOS R because of the many advantages.
Some rumor outlets still push the rumor that Canon might release an APS-C model in the EOS R line-up; that’s not going to happen.
He used the RF 24-105mm f/4L mainly as a landscape lens while capturing Japan’s Fall colors.
In the conclusion Alik says:
The Canon RF 24-105mm f/4 is very sharp with great image stabilization, outstanding contrast and color rendering, nice pop with only some minor yet, easily correctable flaws. Build quality is also really solid and the lens isn’t too heavy either. The best part is the price.
For the landscape, travel photographer, the Instagrammer that wants to shoot a reflection the golden gate bridge through a chain link fence off his smart phone, or whatever it may be, this lens is outstanding for all casual shooting styles.
The lenses main weakness is the f4 aperture. You’ll notice most of [the photos in Alik’s review, editor’s note] are of landscapes and travel. I just haven’t been in love with any portraits I’ve shot. It’s fine for shooting portraits with an awesome backdrop where it’s all about the environment, but when it comes to shooting beauty portraits, you’ll most likely eventually want a faster lens ( faster lens means f2.8 or f2 something like that ).
However, if you’re in a studio shooting models against a backdrop where it’s all about fashion, production design and hair & makeup and less about bokeh, f4 is great. You’ll even get a little more pop if you’re using strobes, which means really stunning, high contrast punchy images. I haven’t tested yet, but I can almost bet you this lens has more pop than the 28-70mm f2 which will need massive glass to produce that aperture. Something to consider if you plan on shooting at f4 or f5.6.
I actually really love this lens, and it’s the first zoom lens I’ve used in a long time where I don’t feel like I’m really compromising quality for versatility. I usually don’t say this in my reviews, but if you’re stepping into the EOS R system, and you don’t have the EF 24-105mm f4, you should seriously consider this lens!
Alik Griffin’s complete review of the Canon RF 24-105mm f/4 comes with a huge set of beautiful sample pictures, and examines thoroughly all aspects of this lens. Be sure to have a look.
It seems that for once they were a bit overwhelmed by Canon’s latest optical masterpiece. From the conclusion:
[…] the R lenses are not only entirely new optics, they are also largely new electrical and mechanical systems. There are a lot of different things in here that we haven’t seen in any Canon EF lenses. Some of them we should have expected, like the increased electronics going to the control ring. Others we don’t really understand yet, like the tension spring in the ring USM motor or the increased electrical shielding.
[…] We also saw lots of new stuff we don’t completely understand yet and a level of complexity we weren’t expecting.
[…] the RF lenses contain some new technology they [Canon, editor’s note] haven’t used before. There’s a lot of engineering that’s gone into these. Things are different inside here. As we’ll see in the next teardown we do, some of that is carrying over to at least some EF lenses. What does this mean? It means Canon has invested very heavily into developing the lenses of the R system. This level of engineering didn’t all happen in the last year, they’ve been working on this for quite a while.
You can see a few images of the teardown below, though I recommend you head over to Lens Rentals for the many pictures and the step by step description of the teardown. Just don’t do it a home yourself.
The Canon RF 50mm f/1.2L is a highly regarded lens, universally seen as one of the two lenses Canon made to showcase the possibilities of their new RF mount (the other one being the RF 28-70mm f/2L.
[…[ it is quite obvious that the Canon RF 50mm f/1.2 USM L is an awesome lens … with a similar awe-inspiring price tag. In relation to other lenses in this class, the performance is already superb at f/1.2. Yes, the outer image region is not truly stellar but it’s impressive nonetheless. The image quality is extreme at medium aperture settings – across the image frame that is. Low lateral CAs contribute to the very high image quality perception. Image distortions are generally no issue. Vignetting is though – at least in its uncorrected state. There is some heavy light-falloff at f/1.2 and f/1.6 but to be fair – that’s to be expected. Most users will not (should not?) buy the lens for its sharpness but for its shallow depth-of-field capabilities. While not truly exceptional, the bokeh is very good with a smooth rendition in the focus transition zone. Out-of-focus highlights are nicely rendered in the image center, less so towards the image corners. However, that’s a physical limitation really. We were also very impressed by the very low bokeh fringing. Yes, you may spot some traces at f/1.2 but it’s not really relevant anymore from f/1.6 onward – and that’s a very rare characteristic. Read the review…
Optical Limits gives it a “highly recommended” rating.
Photography Blog completed their full review of the Canon RF 35mm f/1.8 IS Macro STM lens for the EOS R system. This is the less expensive RF mount lens so far available (£519/€519/$499).
From the conclusion:
There’s lots to like in terms of image quality, and little to complain about. This lens is sharp almost from the get-go, excellent in the centre and at the edges when shooting wide open at f/1.8 and outstanding between f/2.8 and f/11. It’s capable of producing some nice bokeh effects for an f/1.8 lens, helped by the ability to focus as close as 17cms away from your subject. There is some mild barrel distortion and vignetting at f/1.8, but both of these can be corrected in post-processing. Chromatic aberrations are very well controlled and it even produces some nice sun-star effects at f/16-f/22.
The build quality is very good, certainly on a par with the RF 24-105mm kit zoom, with the built-in weather-proofing offering peace of mind in more inclement conditions. Canon also provide a good lens hood and padded case in the box. Read the review…