Canon explains RF lens technology and why bigger is better (sometimes)

degos

EOS 80D
Mar 20, 2015
197
121
The new RF 50mm f1.2 is evidence of what an R lens mount system can do.
Yet Sigma got 99% of the way there with the wider 40mm 1.4 Art on the ancient and useless EF mount, and with a lot less vignetting to boot.

Oh, and at half the price.
 

MayaTlab

EOS 80D
Oct 6, 2015
186
69
Yet Sigma got 99% of the way there with the wider 40mm 1.4 Art on the ancient and useless EF mount, and with a lot less vignetting to boot.

Oh, and at half the price.
More like 120% IMO. The Sigma's performance is quite a bit better off axis (less astigmatism maybe - at least a better point light source performance - and better capacity to carry its central bokeh behaviour to the edges).

Some people, me included, hoped that the new mount would facilitate the design of lenses with lower vignetting, but the 50 RF isn't any better than its predecessor and just like it basically wastes its physical f1.2 aperture as a good part of the frame can't even see it past a typical portrait focusing distance.
 
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KirkD

EOS T7i
Nov 23, 2017
52
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kirkdurston.wixsite.com
Compare it to the Zeiss Otus 55mm for the EF mount.
Stopping the RF 50 f1.2 lens down to f1.4 so I can compare apples to apples, the image quality of the Zeiss 55 f1.4 lens is very slightly better, but the Zeiss is $1,000 more at B&H, does not have autofocus, and does not open up to f1.2. I would like to see what a Zeiss f1.2 would cost if they made one. The Sigma 40mm f1.4 Art is phenomenal, but it might be a bit unfair to compare a lens designed at f1.4 with a lens designed to open up to f1.2. That being said, Sigma is amazing, and really forces the other manufacturers to up their game.
 

Don Haines

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Jun 4, 2012
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Stopping the RF 50 f1.2 lens down to f1.4 so I can compare apples to apples, the image quality of the Zeiss 55 f1.4 lens is very slightly better, but the Zeiss is $1,000 more at B&H, does not have autofocus, and does not open up to f1.2. I would like to see what a Zeiss f1.2 would cost if they made one.
It would certainly cost more than the car that I am driving.......
 

neuroanatomist

I post too Much on Here!!
Jul 21, 2010
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Stopping the RF 50 f1.2 lens down to f1.4 so I can compare apples to apples, the image quality of the Zeiss 55 f1.4 lens is very slightly better, but the Zeiss is $1,000 more at B&H, does not have autofocus, and does not open up to f1.2. I would like to see what a Zeiss f1.2 would cost if they made one. The Sigma 40mm f1.4 Art is phenomenal, but it might be a bit unfair to compare a lens designed at f1.4 with a lens designed to open up to f1.2. That being said, Sigma is amazing, and really forces the other manufacturers to up their game.
In other words, a lens for the EF mount offers equivalent image quality to a similar lens for the RF amount. As I keep saying, I’m still waiting to see (not hear marketing talk about) actual benefits from the short flange distance.

Incidentally, despite the Canon RF 50 mm being f/1.2 and the Zeiss Otis and Milvus 50 mm (-ish) lenses being f/1.4, all three of them deliver the same amount of light, 1.5 T-stops.

I also find it amusing that Canon keeps talking about the ‘larger mount’. The throat diameter of the RF mount is 1 mm larger than that of the EF mount…a whole millimeter, wow, that’s almost a 2% difference!
 
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MayaTlab

EOS 80D
Oct 6, 2015
186
69
The Sigma 40mm f1.4 Art is phenomenal, but it might be a bit unfair to compare a lens designed at f1.4 with a lens designed to open up to f1.2.
Not when a lens vignettes like the 50mm RF.
Vignetting is basically like reducing the aperture in the sagittal and sometimes tangential axis, and cuts the more aberrent light rays in the corners, so vignetting basically facilitates corner performance as well as increases DOF.
The 50mm RF's corners are sufficiently vignetted that they never ever see the lens' physical f1.2 aperture in both axis.
From that perspective while it's certainly a very well corrected lens in the corners, I don't see it as such an impressive feat in light of what the Sigma 40mm achieves. besides, the latter is a wider angle on a more challenging mount, so...

Just a little game, using Mirrorless Comparison's youtube review of the 50mm RF. I've selected their f1.2 and f1.4 samples, turned them to B&W and somewhat harmonised the brightness difference. Then I deliberately put a somewhat small dark circle in the centre of the frame. Now let's play. Which one if the f1.2 shot ? Which one if the f1.4 :D ?

185148
185149

So what is that small circle ? At this focusing distance this is the extent of the image area where you're going to see some difference between f1.2 and f1.4 on the 50mm RF. And note that the above shot is a 16:9 crop for a youtube video, so it's even less of the total area for a 3:2 picture. And even then I don't think that there's a lot of room to pretend that this small difference is going to make the shot - certainly not compared to other areas of bokeh performance.

185150

At short - very short - focusing distances it seems to me that the 50 RF has less vignetting so you may see more tangible benefits to the aperture. But at portrait focusing distances its f1.2 physical aperture is rendered nearly useless by the vignetting.
 
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pixel8foto

EOS M50
Jan 27, 2015
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Also the final sample image (antelope or bighorn sheep grazing in a field) is underexposed and IMO a bad photo - certainly they could have used a better nature photo?
Doesn't look underexposed to me. It looks like the photographer has exposed to keep the colour in the sunset and avoid blowing highlights and then pushed the shadows after. I think I'd make the same choice.
 

jd7

EOS 7D MK II
Feb 3, 2013
719
91
In other words, a lens for the EF mount offers equivalent image quality to a similar lens for the RF amount. As I keep saying, I’m still waiting to see (not hear marketing talk about) actual benefits from the short flange distance.

Incidentally, despite the Canon RF 50 mm being f/1.2 and the Zeiss Otis and Milvus 50 mm (-ish) lenses being f/1.4, all three of them deliver the same amount of light, 1.5 T-stops.

I also find it amusing that Canon keeps talking about the ‘larger mount’. The throat diameter of the RF mount is 1 mm larger than that of the EF mount…a whole millimeter, wow, that’s almost a 2% difference!
I thought the EF and RF mounts are both 54mm diameter? Have I missed something? Is "throat diameter" something different from what I'm talking about?
 
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jd7

EOS 7D MK II
Feb 3, 2013
719
91
The new RF 50mm f1.2 is evidence of what an R lens mount system can do. Check out its image quality here https://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=1225
My take is that the RF 50 f/1.2 is evidence of what a large, heavy and expensive 50mm lens can do these days. Whether it is evidence of what the RF lens mount can do, I'm not so sure. It doesn't seem to be blowing away lenses such as the EF mount Zeiss Otus 55 and the Sigma 50 Art, and as others have said above, optically the Sigma 40 Art seems even better than the RF 50 at a substantially lower price.

At this point, the only thing really interesting me about the R system is the ability to place a focus point just about anywhere in the frame ... and perhaps the slightly smaller and lighter camera body size (although that has disadvantages as well as advantages). Factoring in what I see as disadvantages (lesser battery life, having to use an EVF instead of an OVF (yeah I know some people prefer EVF), most RF native lenses are expensive and bulky), I am very happy sticking with DSLRs and the EF system for the time being.
 
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Kit.

EOS 6D MK II
Apr 25, 2011
1,089
518
I also find it amusing that Canon keeps talking about the ‘larger mount’. The throat diameter of the RF mount is 1 mm larger than that of the EF mount…a whole millimeter, wow, that’s almost a 2% difference!
I don't see Canon talking about a 'larger mount'. I see Canon talking about a 'large mount' allowing to put a large glass element closer to the sensor.
 
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neuroanatomist

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Jul 21, 2010
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I thought the EF and RF mounts are both 54mm diameter? Have I missed something? Is "throat diameter" something different from what I'm talking about?
Nope, I’ve missed something. Thanks fir the correction! You’re right, same diameter for EF and RF. (I was recalling that the Nikon Z mount is 1 mm larger in diameter.)

Makes the discussion of the ‘larger mount’ more ridiculous, as it pertains to ‘advantages’ over the EF mount, as some here claim (without evidence). Obviously the RF mount is larger than Sony’s E-mount.
 
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neuroanatomist

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I don't see Canon talking about a 'larger mount'. I see Canon talking about a 'large mount' allowing to put a large glass element closer to the sensor.
Not Canon. Forum members.

Even this main forum post (and thread) by CRguy started with, “Canon once again talks about the benefits of the bigger diameter RF mount...”
 
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Normalnorm

EOS 7D MK II
Dec 25, 2012
501
102
The evidence: the exceptional quality achieved by Leica with wide -angle lenses, the Leica R lenses were always far behind (corner sharpness, contrast, etc...)
I've never had a DSLR lens that was as good as the 18, 21, 24, 28 & 35 mm Asph. M lenses, not even a Zeiss or a Canon. (Yes, I know, this isn't scientific).
Is the short flange distance the main reason ? I tend to believe it has at least a part to play, according to the Leica opticians, it definitely has!
The challenge for the M lenses is that they were designed for film. On digital sensors other than Leica M series cameras the IQ at the edges suffers. If Canon were to make tiny little manual focus lenses with no IS they would still have the hurdle of edge smearing.
 

koenkooi

EOS RP
Feb 25, 2015
346
197
Nope, I’ve missed something. Thanks fir the correction! You’re right, same diameter for EF and RF. (I was recalling that the Nikon Z mount is 1 mm larger in diameter.)

Makes the discussion of the ‘larger mount’ more ridiculous, as it pertains to ‘advantages’ over the EF mount, as some here claim (without evidence). Obviously the RF mount is larger than Sony’s E-mount.
ISTR that Canon said things like the electronic contacts were smaller so that the RF has more useable space while keeping the same diameter. I can't check that myself since I don't have a FF EF mount camera.
 

neuroanatomist

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Jul 21, 2010
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ISTR that Canon said things like the electronic contacts were smaller so that the RF has more useable space while keeping the same diameter. I can't check that myself since I don't have a FF EF mount camera.
The contact area seems to protrude about the same distance into the mount on my R and 1D X. The no-mirror box on the R definitely looks spacious, though.
 
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Architect1776

Defining the poetics of space through Architecture
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I would like to see Canon do like they did with many EFS lenses. There are some very sharp ones but inexpensive (10-18mm) and this could be translated into the RF mount. Most of us do not need the built like a tank lens just a good quality optically. Take out the IS once the IBIS is available in all the lenses that do not fully benefit from IS and IBIS is just fine. I would then like to see the lenses come down substantially in size and weight. Look at the old FD lenses for size inspiration, the FD 80-200mm is petite compared to the EF equivalent today. I have no problem with f4 lenses as we have insanely high ISOs available now. How did we ever survive with Kodachrome 64 and the slow lenses of the same period? Great shots were made then through real skill and talent.
Bottom line I would like smaller very sharp not super large aperture lenses to match the RF mount.
 
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BillB

EOS 6D MK II
May 11, 2017
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Not Canon. Forum members.

Even this main forum post (and thread) by CRguy started with, “Canon once again talks about the benefits of the bigger diameter RF mount...”
Canon talks about the mount permitting larger diameter lens elements closer to the lens, which would be the result of the shorter flange distance, since the RF mount opening is the same size as the EF. One effect is that the front lens can be smaller than that of comparable EF lenses. The difference between the front lens size of the RF 35 f1.8 and the EF 35 f2.0 is striking.
 
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neuroanatomist

I post too Much on Here!!
Jul 21, 2010
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Canon talks about the mount permitting larger diameter lens elements closer to the lens, which would be the result of the shorter flange distance, since the RF mount opening is the same size as the EF. One effect is that the front lens can be smaller than that of comparable EF lenses. The difference between the front lens size of the RF 35 f1.8 and the EF 35 f2.0 is striking.
Yes, with the RF version of the 35mm, Canon has managed to dramatically reduce the size of the front element compared to the EF 35/2 IS. In fact, they’ve managed to make the front element about as small as the one on the old EF 35/2 non-IS...

Now, you were saying something about the advantages of the RF mount? :unsure:
 

BillB

EOS 6D MK II
May 11, 2017
1,052
286
I would like to see Canon do like they did with many EFS lenses. There are some very sharp ones but inexpensive (10-18mm) and this could be translated into the RF mount. Most of us do not need the built like a tank lens just a good quality optically. Take out the IS once the IBIS is available in all the lenses that do not fully benefit from IS and IBIS is just fine. I would then like to see the lenses come down substantially in size and weight. Look at the old FD lenses for size inspiration, the FD 80-200mm is petite compared to the EF equivalent today. I have no problem with f4 lenses as we have insanely high ISOs available now. How did we ever survive with Kodachrome 64 and the slow lenses of the same period? Great shots were made then through real skill and talent.
Bottom line I would like smaller very sharp not super large aperture lenses to match the RF mount.
The RP gives hope that some less expensive lenses may show up, as does the RF 35 f1.8. However these lenses are likely to be larger than an EFS 10-18. A lens equivalent to an EFS 10-18 that would cover a FF sensor would be 16-29. Even with variable maximum aperture this would be a larger and likely more expensive lens than the 10-18. For EF-S and EF-M size and prices, APS-C sized sensor coverage is part of the deal.