The benefits of the large diameter of the EOS R’s RF mount explained

4fun

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Nov 19, 2018
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What I’m seeing with all the illustrations here, and elsewhere, is an exaggeration of the size of elements for lens designs for mirrorless. The reality isn’t so exaggerated.

not sure about this - whether or not illustrations and images truly "to scale" ... or not.

illustration and images of the 2 lenses seem to correspond pretty well. does not look "exaggerated" to me.

24_o.jpg



waiting to read reports of "scratched rear lenses". oO
 
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jd7

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Feb 3, 2013
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actually, the diameter *IS* very important. it's a combination of lens registration distance and mount diameter that gives the flexibility.

which is why they didn't use the EF-M mount. they could use the EF-M mount, and the article states that Canon even considered it.

the larger mount diameter allows them to "flip" the elements around, and not use an element to "spread" the light across the entire sensor.

This is why when I wrote CN's article, I compared the RF lens to a similar Sony FE lens, and the differences are as Canon discussed in their presentation.
Agree with all of that but I think there has been some confusion around the internet about whether the RF mount is larger than the EF mount. I've seen a few people claim that it is, but of course it isn't - it's the same size as the EF mount. I'm guessing that a few people have jumped to the conclusion that since Nikon just introduced a FF mirrorless camera with a mount larger than its previous FF mount, Canon must have done the same thing with their new FF mirrorless. Anyway, my assumption is the earlier posters were picking up on the sorts of claims I've seen elsewhere and feeling like references to the new RF mount being "large" tend to reinforce that misinformation. Your point is quite different though of course - you are just saying the EF/RF mount is larger than the EF-M mount.
 
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4fun

picture? perfect!
Nov 19, 2018
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Your point is quite different though of course - you are just saying the EF/RF mount is larger than the EF-M mount.

more importantly:
* Canon EF and R mount parameters [combo of throat width and flange focal distance] are very well chosen for FF image circle.
* Sony E-mount is well chosen for APS-C sensor image circle but a very poor choice for FF sensors.
* Nikon Z mount looks a bit of overkill for throat width. Apparently Nikon wanted to have potential for some exotic ultra-fast "showcase" glass [eg manual focus f/0.95 lenses]. Regular lenses will generally not profit from it.
* Canon EF-M is perfectly chosen for APS-C sensor [Canon 1.6x] but would be a very bad choice for FF image circle.

Agree with all of that but I think there has been some confusion around the internet about whether the RF mount is larger than the EF mount. I've seen a few people claim that it is,
Folks who don't even know the basic mount parameters [not you!] should first read up on the subject before posting.
 
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LDS

Sep 14, 2012
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since Nikon just introduced a FF mirrorless camera with a mount larger than its previous FF mount

Nikon was still constrained by compatibility with its old F mount. Canon broke compatibility with the previous FD mount more than 30 years ago and increased the diameter back then. Going even larger would mean also larger cameras, or a new camera design. And may be not needed (yet?)
 
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4fun

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I was surprised to see the ef 85mm f1.4 LIS launched. I was expecting a slew of new f1.2 lenses (24mm / 35mm / 50mm and 85mm). So I wonder if Canon are holding back the f1.2 feature for the R mount lenses. Purely for a marketing purpose (there really isn't a technical or optical reason).

but there is a fairly compelling economic reason. Even in the past a few drooled over f/1.2 lenses, but only very few were sold ... compared to more sensible lens alternatives. Now, with EOS R system launched, exotic-expensive EF lenses will be an even harder sell. So I would not hold my breath for any new/additional f/1.2 EF lenses. As a matter of fact I expect hardly any new/additional EF lenses to appear.
 
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but there is a fairly compelling economic reason. Even in the past a few drooled over f/1.2 lenses, but only very few were sold ... compared to more sensible lens alternatives. Now, with EOS R system launched, exotic-expensive EF lenses will be an even harder sell. So I would not hold my breath for any new/additional f/1.2 EF lenses. As a matter of fact I expect hardly any new/additional EF lenses to appear.

The f/1.2 lenses sold more than "very few." They were staples for event and portrait photographers.
 
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It's only a mater of time before less expensive Ti7 level cameras are produced using the RF mount. With judicious use of plastic and the sizes of the elements the lenses could be made cheaper, especially if they use a smaller sensor size. Add in the existing aps-c sensors or a new line of aps-h sensors to differentiate between full frame and consumer RF mount cameras and it gets even cheaper.

A aps-h sized sensor might even be a great fit with a 7dII replacement. Less data to process, still less detail than a 1dx replacement.
 
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not sure about this - whether or not illustrations and images truly "to scale" ... or not.

illustration and images of the 2 lenses seem to correspond pretty well. does not look "exaggerated" to me.

24_o.jpg



waiting to read reports of "scratched rear lenses". oO

Well, you’ll see right there, that the difference in rear element size isn’t that different. Assuming that the pics of both lenses are real. We’re seeing an exaggeration of what’s possible in the drawings of the lens designs.

It’s simple arithmetic. Look at the rear of your lens, and see the max diameter element that can fit, minus the metal construction of the lens barrel holding the lenses in place. It’s much smaller than the front elements of a number of current fast lenses. It’s a physical limitation. If they made the mount with a gigantic 70mm size, they could do it. But as it is, the mount is about the same dia as before, just a lot closer.
 
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Nov 2, 2016
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I was surprised to see the ef 85mm f1.4 LIS launched. I was expecting a slew of new f1.2 lenses (24mm / 35mm / 50mm and 85mm). So I wonder if Canon are holding back the f1.2 feature for the R mount lenses. Purely for a marketing purpose (there really isn't a technical or optical reason).

Canon has to be realistic about sales. With the new 50 1.2 going for $2,300, how many do they really expect to sell? That and the f2 zoom are more of a; “See what we can do!”. But to sell tens, and even hundreds of thousands of lenses, they need much lower pricing. Really, 1.4 is just a half stop slower, but lenses could cost just half of what the 1.2 versions could cost. F1.2 lenses have always been lenses we generally lusted over, but never bought new.
 
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Bob Howland

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Small percentage of sales but that could be said of any L lens besides the kit lenses. A small percentage does not mean "a few."
Really?? Wild guess: There are five times as many 16-35 f/2.8, 24-70 f/2.8 and 70-200 f/2.8 IS lenses sold as there are any f/1.2 lens. Does anybody here have real data?
 
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CR guy didn't write the article, so he can't change it. Besides, you and degos misinterpret the point anyway.

They could have titled THIS article: "reduced flange distance combined with keeping the same, large mount diameter..." // This article title just keeps this false notion circulating that RF went up in diameter from EF.
 
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