Patent: Optical formulas for a trio of wide f/1.8 prime lenses for the RF-S mount

[LogicExtremist]

Would porting most/all the m-mount lenses to rf mount suffice?

Why not port the best of EF-S and EF-M to RF-S? Even better, with improvements, even minor ones. Making the new RF-S platform better than either of its predecessors would be a positive development and a step in the right direction. The other possibility is that they could make minimal effort and put out the least number of lenses possible because they just want to sell expensive premium gear as it's more profitable.

 

[Bob Howland]

Why not port the best of EF-S and EF-M to RF-S? Even better, with improvements, even minor ones. Making the new RF-S platform better than either of its predecessors would be a positive development and a step in the right direction. The other possibility is that they could make minimal effort and put out the least number of lenses possible because they just want to sell expensive premium gear as it's more profitable.

"Porting" M-mount and EF-S lenses means two different things. Current owners of EF-S lenses can "port" those lenses with a $100 adapter. Porting an M-mount lens is both simpler and more complicated. All you have to do is look at pictures of the two 18-150 lenses side-by-side to see why.

 

[LogicExtremist]

"Porting" M-mount and EF-S lenses means two different things. Current owners of EF-S lenses can "port" those lenses with a $100 adapter. Porting an M-mount lens is both simpler and more complicated. All you have to do is look at pictures of the two 18-150 lenses side-by-side to see why.

I meant exactly what you meant, not adapting, but porting, that is, taking all the front lens element group optics and adding the necessary rear lens element group to optimise it for the RF-S mount.

 

[EOS 4 Life]

Still no ultra wide angle RF-S lenses though.
IMHO, RF-S lenses will be made to suit the build/cost/etc level of the lower end R mount bodies so f1.8 seems to be different to that assumption.

I would be very surprised to see a RF-S lens that was L quality for instance. Has any EF-S lens been wider than f2.8?

The current non-L full-frame f/1.8 prime lenses are fairly cheap.
I would expect APS-C versions to cost significantly less.
I would not expect them to be L quality either.

Primes of f/2.8 and f/3.5 would not surprise me either.

 

[Chaitanya]

The current non-L full-frame f/1.8 prime lenses are fairly cheap.
I would expect APS-C versions to cost significantly less.
I would not expect them to be L quality either.

Primes of f/2.8 and f/3.5 would not surprise me either.

16mm f2.8 is a great option for APS-C RF bodies its cheap, small and has decent max mag ratio.

 

[BakaBokeh]

Would porting most/all the m-mount lenses to rf mount suffice?

That would be a good start. The 22m f2 and 32mm f1.4 blows my mind how I can have these fast apertures in a small package. I was very hopeful for more. If they do port these over to RF-S hopefully, they can build on it and develop more fast primes at other focal lengths.

 

[EOS]

Well, a 24 f/1.8 RF lens is about ready to hit the streets, so there is that.

Is that the RF 24mm IS STM Macro? Not exactly the 24mm L we’ve been waiting for. ¯\_(ツ)_/¯

 

[SnowMiku]

Would porting most/all the m-mount lenses to rf mount suffice?

I'm thinking that could be the plan, port all of the EF-M lenses to RF-S and then if demand goes down on EF-M too much in a few years time then RF-S will be the direct replacement.

 

[SnowMiku]

The EF-S 10-8mm and 55-250mm were lenses that punched well above their weight, and provided great image quality for their price. Even if Canon didn't put metal lens mounts on either (to remind buyers they're using a cheaper lens) those lenses really delivered. It would be great to see RF-S versions with some kind of improvements (and not darker in aperture) at such good prices.

The plastic mounts personally never bothered me. It would be nice to see RF-S lenses being improved over the EF-S and EF-M versions but unfortunately I think they are going to have less range and be darker such as the RF-S 18-45mm F4.5-6.3 IS STM vs EF-M 15-45mm f/3.5-6.3 IS STM vs EF-S 18-55mm F/3.5-5.6 IS STM.

 

[neuroanatomist]

The plastic mounts personally never bothered me. It would be nice to see RF-S lenses being improved over the EF-S and EF-M versions but unfortunately I think they are going to have less range and be darker such as the RF-S 18-45mm F4.5-6.3 IS STM vs EF-M 15-45mm f/3.5-6.3 IS STM vs EF-S 18-55mm F/3.5-5.6 IS STM.

I think most will be identical, like the RF-S 18-150 and EF-M 18-150.

The standard zoom lens was an exception, IMO, required because the EF-M 15-45 was not a retrofocal design with the 18mm flange focal distance on M, but would need to be with the 20mm distance on R. The other EF-M designs should port over directly.

 

[Bob Howland]

I meant exactly what you meant, not adapting, but porting, that is, taking all the front lens element group optics and adding the necessary rear lens element group to optimise it for the RF-S mount.

If Canon follows Sigma's example, there won't be any rear element group. They'll just extend the rear of the lens and effectively make the adapter a permanent part of the lens.

 

[neuroanatomist]

If Canon follows Sigma's example, there won't be any rear element group. They'll just extend the rear of the lens and effectively make the adapter a permanent part of the lens.

I highly doubt Canon will release RF-S lenses that are simply EF-S lenses with 24mm of empty barrel at the rear. EF-M lenses, yes – a new barrel and mount with the same optics inside will work for most of them.

 

[amfoto1]

Is there such a thing as an "RF-S mount"?

I thought that "RF-S" lenses would fit on normal RF mount, as well as on crop cameras, but that full-frame models would electronically recognise RF-S lenses, and crop the frame accordingly?

Or have I got it wrong?

There is no RF-S mount... But there are RF-S lenses.
With their DSLRs Canon felt the needs to prevent the "crop only" lenses from being fitted to their full frame cameras. Remember that at the time, in 2004, Canon was almost the only company making both APS-C and full frame cameras (Nikon had made one full frame by then, if I remember correctly). So the distinction may have been more necessary.
Today most photographers advanced enough to be buying interchangeable lens cameras understand the distinction. Plus with mirrorless there is no concern about possible interference between the rear element of the lens and a moving mirror, as there could have been with DSLRs.
So there is no need for a distinct mount with the R-series. But there is still need for at least some "crop sensor designed" lenses, which Canon is designating RF-S.

 

[amfoto1]

I am not so sure these patents are for RF-S lenses. I think they may be full frame capable RF.

The reason I think so is the stated "half angle of view" of each lens. Take the 24mm as an example. A full frame 24mm lens has roughly 82 degree angle of view and the patent states exactly half that: 41 degrees.

Why do you think these are RF-S lenses?

Further, I think the most likely next RF-S lens would be an ultrawide zoom and there has been a 10-24mm on the official RF lens roadmap since the beginning.

Plus, I would hope Canon simply incorporates some of the very good EF-M lens optical designs, such as the 22mm f/2 "pancake". However, it's not just a matter of putting the EF-M optics into a new RF barrel. The EF-M back focus is shorter than the RF mount. EF-M is 18mm while RF is 20mm. So some tweaking will be required. (The back focus on EF & EF-S is 44mm, leaving plenty of room... 24mm... for an adapter.)

 

[neuroanatomist]

TL;DR - these are RF lenses, not RF-S (but not for the reason suggested by @amfoto1 )

I am not so sure these patents are for RF-S lenses. I think they may be full frame capable RF.

I agree that these are RF (full frame) designs, but not for the reason you suggest.

The reason I think so is the stated "half angle of view" of each lens. Take the 24mm as an example. A full frame 24mm lens has roughly 82 degree angle of view and the patent states exactly half that: 41 degrees.

That’s why it’s called a half angle of view. Canon’s optical design patents specify angles, element curvatures, etc., for just half a lens because lenses designs are symmetrical. A lens design with a specified half angle of view of 41° has a full AoV of 82° as you’d expect for a 24mm lens.

Also, lens design parameters like focal length and AoV (or hAoV) are intrinsic to the lens – they don’t get adjusted based on the sensor size for which the lens is intended.

Why do you think these are RF-S lenses?

They are suggested to be RF-S because of the image height, which is the radius of the image circle (1/2 the diagonal of the intended sensor). A FF sensor has a 43.2mm diagonal, meaning FF lens designs have an image height of 21.6mm. These designs all fall short of that value, meaning the image circles won’t fully cover a FF sensor.

However, an APS-C image circle is 31.2mm in diameter, meaning a 15.6mm image height – these lenses all have images circles too big for APS-C. In wide angle lenses like these, the image circle is limiting (it’s not for telephoto lenses, which is why there aren’t EF-S telephoto lenses). If these are RF-S lenses, too-large image circles mean lenses that are unnecessarily larger and heavier. Canon may not care about that, but more glass and more plastic than minimally needed means higher production costs and thus lower profits – and for damn sure Canon cares about that.

Some time back, CRguy posted about patents for RF APS-C pancake lenses. The lens that CRguy called an RF-S 16mm f/2.8 has an image height of 18.2mm, and in fact that patent design is the RF 16mm f/2.8 lens that can be purchased today (which is obvious when the lens diagram from the patent example is superimposed on the block diagram of the actual RF lens).

The reason the image circle can be too small for FF is that the lenses have significant geometric (barrel) distortion in the design. Correcting barrel distortion stretches the corners of the image, so after correction the FF corners will be filled in, just as they are on the 16/2.8.

 

[Czardoom]

Why not port the best of EF-S and EF-M to RF-S? Even better, with improvements, even minor ones. Making the new RF-S platform better than either of its predecessors would be a positive development and a step in the right direction. The other possibility is that they could make minimal effort and put out the least number of lenses possible because they just want to sell expensive premium gear as it's more profitable.

Or the other - perhaps most likely alternative - is that they could make minimal effort and produce less RF-S lenses because they know from past experience and market research, that the target consumer for crop cameras is either an entry level consumer looking for only the basic lenses and wants them cheap in price, or they are birders and wildlife shooters who will be buying RF not RF-S lenses.

 

[masterpix]

That's correct. However, I expect we will see a lot of people/sites referring to RF-S lenses as having an RF-S "mount." Not entirely accurate, but Canon Rumors has never claimed to be a research paper.

It is the same like the older EF and EFs which has the same mount but different "image width". As the EF and EFs also somewhat differ cause in the EFs it was able to "penetrate" deeper into the camera mount for the APS-C mirror was a bit smaller and therefore left bit more room inside. In the case of the RF, it won't be as such for the space behind the mount it similar in all models. So the RFs lenses differs from the RF is by the "image width" alone.

 

[neuroanatomist]

Just in case there was any doubt that the lenses in this patent are RF lenses and not RF-S lenses, here is the 24mm f/1.8 diagram from the lens patent:


And here is the block diagram of the RF 24mm f/1.8 lens that is now available for purchase.

 

[chasingrealness]

I decided to take the plunge and buy the R7 today. Professional obligations are increasing again and while I’ve always found my RP adequate for all my client work to date?m, two bodies, multiple card slots, and light video capabilities are a must for my second body. I’m just glad the R7 exists during this time that I’m priced out of anything more premium.