Lens design comparison: Canon EF 50mm f/1.8 STM and the Canon RF 50mm f/1.8 STM

slclick

Pinhole
Dec 17, 2013
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Hasn't every iteration of the Nifty Fifty been a simplistic and low end engineering cost retooling? Oh and as for Prime niches, I live in the 40/135 niche group. I don't do 50mm, 40 just feels right to me. What's that? I should just take a few steps back?
 

lawny13

EOS M6 Mark II
Mar 6, 2019
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It is just the standard Double-Gauss design that has been around in innumerable formulae's since 1817.


Uncle Roger has a great series of articles on optical designs too.


What I actually find interesting is the element offset, the RF lens elements are set further forwards than the EF version and are an effective 'adapter', they are not using the advantages of the shorter flange distance here one bit, merely rejigging the thing to do the same. I'd expect performance to be somewhere between the EF 1.8 and EF 1.4, the key will be the way they have used the special element in green.
That isn't how lens design works. The centre of the lens elements for a lens of 50 mm FL needs to be about 50 mm away from the focal plane in a design that is as simple as possible. This is why it is the wider angles that tend to get smaller on mirrorless because the flange distance is smaller.

Additional glass is needed. when this FL to focal plane deviates.

Why do you think that the 70-200 nikon and sony lenses are about the same size as the DSLR ones? Why do you think the 50s are bigger than the nifty fifties from the DSLR cameras? Though the canon 70-200 is small when zoomed out it is about the same size as the rest zoomed in.

What canon can gain from the flange distance though is the fact that the rear lens can be bigger, and thus it should allow for better sharpness across the frame.

If this 50 is sharp wide open, and sharp in the corners it is already big gain over the EF50 stm. If it were quite as well.... that would be great.
 
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dwarven

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Dec 12, 2019
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I bet it will be $250. If it's sharper at f/1.8 than the EF version then it will be worth it. The one I have is quite smooshy wide open.
 

privatebydesign

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That isn't how lens design works. The centre of the lens elements for a lens of 50 mm FL needs to be about 50 mm away from the focal plane in a design that is as simple as possible. This is why it is the wider angles that tend to get smaller on mirrorless because the flange distance is smaller.

Additional glass is needed. when this FL to focal plane deviates.

Why do you think that the 70-200 nikon and sony lenses are about the same size as the DSLR ones? Why do you think the 50s are bigger than the nifty fifties from the DSLR cameras? Though the canon 70-200 is small when zoomed out it is about the same size as the rest zoomed in.

What canon can gain from the flange distance though is the fact that the rear lens can be bigger, and thus it should allow for better sharpness across the frame.

If this 50 is sharp wide open, and sharp in the corners it is already big gain over the EF50 stm. If it were quite as well.... that would be great.
Canon have made a cheap lens cheaply, which I am not criticizing them for by the way. They have taken a tried and true design and made modest optical formula changes despite the fact they had the opportunity to reinvent the wheel with a different mount.

The rear element is slightly larger in the new lens if the diagrams are to scale, and I would expect the RF 50 f1.8 to be an improvement over the EF version. But come on, designing a Doube-Gauss 50mm lens isn't rocket science even if you have the chance to throw in a moulded aspherical element, even the much maligned EF 50 f1.4 is sharper than the 100 L Macro at f5.6. That lens design has built in limitations as explained in the article I previously linked to, it is an interesting read.
 

lawny13

EOS M6 Mark II
Mar 6, 2019
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Canon have made a cheap lens cheaply, which I am not criticizing them for by the way. They have taken a tried and true design and made modest optical formula changes despite the fact they had the opportunity to reinvent the wheel with a different mount.

The rear element is slightly larger in the new lens if the diagrams are to scale, and I would expect the RF 50 f1.8 to be an improvement over the EF version. But come on, designing a Doube-Gauss 50mm lens isn't rocket science even if you have the chance to throw in a moulded aspherical element, even the much maligned EF 50 f1.4 is sharper than the 100 L Macro at f5.6. That lens design has built in limitations as explained in the article I previously linked to, it is an interesting read.
Look... personally I loved the ZA 55. I had hoped that canon would give me a good quality weather sealed and internally focusing 50. The ZA 55 was my walk around lens when I had the A7III, and I was wishing for a good one for RF. So... I am disappointed. My comment was mainly that it wasn't about moving the elements forward to have an adapter built in, but with this simple design the lens internals simply need to be moved forward.

If canon doesn't give us a sharp, good 50. Then I will basically keep my EF stm adapted and just wait for a sigma or Tamron 50 prime to appear for the RF system down the road. I have bigger fish to fry, like the RF 100-500 and the RF 70-200.
 

jolyonralph

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I must admit I was hoping for something a bit more modern - something closer to the Sony/Zeiss 55mm FE lens which has 7 elements including a concave front element looks like this is going to be pretty close to the current 50mm EF lens in quality. But if it's cheap that's not a bad thing, but I think anything over $200 is going to be too much.
 

privatebydesign

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Hasn't every iteration of the Nifty Fifty been a simplistic and low end engineering cost retooling? Oh and as for Prime niches, I live in the 40/135 niche group. I don't do 50mm, 40 just feels right to me. What's that? I should just take a few steps back?
No.

And no. I have zooms, I have primes, my most used lenses are manual focus TS-E primes, when I get an R5 it will be accompanied by the bargain 35 and 85 primes. But that doesn’t change the numbers, nor the economics when looked at from Canon’s perspective, as I said, I doubt we will ever have the breadth of lenses in the RF line we had in the EF line not least of which reasons is because it spanned such a developmental era of the camera industry.

The FL saw little comparative change, the FD went from the FL manual everything to auto aperture with a single failed stab at AF. The EF went from 135 format film through three different sized digital sensors and pioneered fully electronic communications, step less apertures, leading AF and IS, CAD, more development in exotic glass and molded aspheric lenses than you could shake a stick at and is current and world class even now three decades later.
 
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stevelee

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Hasn't every iteration of the Nifty Fifty been a simplistic and low end engineering cost retooling? Oh and as for Prime niches, I live in the 40/135 niche group. I don't do 50mm, 40 just feels right to me. What's that? I should just take a few steps back?
The idea is that a “normal” lens has a focal length equal to the diagonal of the sensor size. For “full frame” that is about 43mm. So it should be no surprise that 40mm seems more “normal“ to you than does 50mm. My first 35mm camera was a Yashica rangefinder camera with a 45mm lens. I took many of the best pictures I have ever taken with that camera. Because I was using the same focal length all the time, I didn’t have to put the camera up to my eye to focus the shot. It was almost like I had that frame in my brain and could look at the world that way. I eventually realized that a great benefit of doing photography for me was in how I see things, perceiving beauty or order in the ordinary.
 

stevelee

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I bought the EF 50mm f/1.4 to use on my T3i as a portrait lens more than anything else. It worked great for that purpose, and I didn’t experience anything that would justify complaints like I read here about that lens. If it is not terribly sharp in the corners, I would know about that, for example. I was using a crop sensor, so I wasn’t seeing the corners of FF. Also, in portraits, soft corners at most are a feature and not a bug. I don‘t recall the actual complaints, just that there is a lot of poopooing that lens.

Since I got the 6D2, I have not had occasion to use that lens. I don’t know what I’d need it for. My 85mm f/1.8 has taken over what I was using it for, and my kit zoom covers that focal length. It may be that I zoom to c. 50mm reasonably often, but I’m unaware of it. So I really can’t relate to the frequent laments here for 50mm lenses to suit various tastes.
 

slclick

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Dec 17, 2013
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No.

And no. I have zooms, I have primes, my most used lenses are manual focus TS-E primes, when I get an R5 it will be accompanied by the bargain 35 and 85 primes. But that doesn’t change the numbers, nor the economics when looked at from Canon’s perspective, as I said, I doubt we will ever have the breadth of lenses in the RF line we had in the EF line not least of which reasons is because it spanned such a developmental era of the camera industry.

The FL saw little comparative change, the FD went from the FL manual everything to auto aperture with a single failed stab at AF. The EF went from 135 format film through three different sized digital sensors and pioneered fully electronic communications, step less apertures, leading AF and IS, CAD, more development in exotic glass and molded aspheric lenses than you could shake a stick at and is current and world class even now three decades later.
I see where you are coming from except for where you missed one of my words. Nifty.
 

canonnews

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What canon can gain from the flange distance though is the fact that the rear lens can be bigger, and thus it should allow for better sharpness across the frame.

If this 50 is sharp wide open, and sharp in the corners it is already big gain over the EF50 stm. If it were quite as well.... that would be great.
yeah I admire your enthusiasm and positive outlook, but if canon wanted a sharp wide open lens, it wouldn't be a 6 element design. it also doesn't have the "RF classical" large rear element design either. it's basically 30-35mm backfocus distance lens dovetailed for the RF mount.
 
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Tangent

EOS 90D
Nov 13, 2015
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yeah I admire your enthusiasm and positive outlook, but if canon wanted a sharp wide open lens, it wouldn't be a 6 element design. it also doesn't have the "RF classical" large rear element design either. it's basically 30-35mm backfocus distance lens dovetailed for the RF mount.
Along that train of thought... I was scanning the 50 1.8 EF STM reviews on B&H and found four leading quality complaints in the 1 and 2 star reviews to be: noisy AF, manual focus ring dodgy in use, lens hard to mount on camera, and, as mentioned, lens soft. It will be interesting to see if Canon addressed these other three quality "opportunities" as well.
 

lawny13

EOS M6 Mark II
Mar 6, 2019
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I must admit I was hoping for something a bit more modern - something closer to the Sony/Zeiss 55mm FE lens which has 7 elements including a concave front element looks like this is going to be pretty close to the current 50mm EF lens in quality. But if it's cheap that's not a bad thing, but I think anything over $200 is going to be too much.
I do am fine with that, but then my opinion is that canon should also have a mid range option sometime. 200 vs 2700 dollar options is a massive gap. Same goes for size. Think they would be able to sell a good F1.4 well. In particular to R6 and R5consumers
 

mb66energy

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Dec 18, 2011
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yeah I admire your enthusiasm and positive outlook, but if canon wanted a sharp wide open lens, it wouldn't be a 6 element design. it also doesn't have the "RF classical" large rear element design either. it's basically 30-35mm backfocus distance lens dovetailed for the RF mount.
I am another person who thinks that this lens will be a very good lens in absolute terms:
The upcoming RF 50 has only 6 elements and 5 groups so contrast will be really good (if they use high quality coatings) but correction will be at a slightly lower level compared to e.g. an RF 50 1.2. Why slightly? An aspherical element is essential to make a reasonably good f/1.2 lens (EF 50 f/1.2) but it will enable a very good f/1.8 max aperture!
Spherical aberration (due to the typical spherical lens surfaces) is the strongest enemy for high aperture lenses at high apertures and he best antidote is ... an aspherical lens.
 

Antono Refa

EOS R
Mar 26, 2014
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That isn't how lens design works. The centre of the lens elements for a lens of 50 mm FL needs to be about 50 mm away from the focal plane in a design that is as simple as possible. This is why it is the wider angles that tend to get smaller on mirrorless because the flange distance is smaller.
I'm far from being an expert, but shouldn't it be the aperture, rather than the center of the lens elements?

Additional glass is needed. when this FL to focal plane deviates.

<snip>

What canon can gain from the flange distance though is the fact that the rear lens can be bigger, and thus it should allow for better sharpness across the frame.
My impression was the additional glass would not be needed for the FL range between RF's 20mm and EF's 44mm.
 

WoodyWindy

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Jul 20, 2010
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Interesting discussion. As with a few others, I immediately honed in on the facts that
1. the whole set of elements was shifted "outward" to stay very close to the same focal plane distance.
2. the "inner" groupings are inverted compared to the classic design.
3. the actual silhouettes clearly show differences.

I don't have the optics expertise to know exactly how these changes affect the resultant image, but Canon is not known for making changes for their own sakes. We have to assume we're going to see some pretty significant improvement over the classic 50 f1.8 offerings.
 

jolyonralph

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Interesting discussion. As with a few others, I immediately honed in on the facts that
1. the whole set of elements was shifted "outward" to stay very close to the same focal plane distance.
2. the "inner" groupings are inverted compared to the classic design.
3. the actual silhouettes clearly show differences.

I don't have the optics expertise to know exactly how these changes affect the resultant image, but Canon is not known for making changes for their own sakes. We have to assume we're going to see some pretty significant improvement over the classic 50 f1.8 offerings.
There are two reasons to change a design that's worked well in the past - one is to improve quality and the other is to reduce production cost. Or, very occasionally, both.