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

The fact that the elements are offset to the front illustrates the thinness of the argument that mirrorless bodies will always give us smaller, lighter lenses. Some designs may benefit but even the WA lenses are not seeing the dramatic reduction in mass that was promised.

Sporgon said:

Do designs that have worked well in the past still meet the demands and expectations required to be considered as working well to day ?

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privatebydesign said:

For photographers, almost without exception, YES. For forum nerds, self appointed YouTube experts, ‘reviewers’, and people that just love to argue, no.

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But what about lens design rot? I'm sure I've seen designs rot with age.

(And yes, I guess that makes me a "people that just love to argue" even if only in jest.)

I hope it would be compatible with es-68 lens hood

jolyonralph said:

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.

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The classic 50 f1.8 optical formula is as old as the hills, and has been applied to/reused in multiple generations and iterations of this lowest-cost prime lens in the EF series, including the post-digital age. You could say, it is "well proven", and is probably VERY cost effective to produce. Therefore, the low-cost option for a native RF mount version would have stopped at shifting the optics out, and fixing up the mount.

Canon didn't do that. Instead, here there is clear evidence of substantial work on the optical formula. That bodes well for improvement in the output, including both the image quality (aberrations, vignetting) at the edges, probably overall color/contrast, and I would guess minimum focus distance as well. (how many folks have inverted a 50 f1.8 to create an "instant" macro lens?)

In the end, I'm excited to see what this baby can do.

WoodyWindy said:

The classic 50 f1.8 optical formula is as old as the hills, and has been applied to/reused in multiple generations and iterations of this lowest-cost prime lens in the EF series, including the post-digital age. You could say, it is "well proven", and is probably VERY cost effective to produce. Therefore, the low-cost option for a native RF mount version would have stopped at shifting the optics out, and fixing up the mount.

Canon didn't do that. Instead, here there is clear evidence of substantial work on the optical formula. That bodes well for improvement in the output, including both the image quality (aberrations, vignetting) at the edges, probably overall color/contrast, and I would guess minimum focus distance as well. (how many folks have inverted a 50 f1.8 to create an "instant" macro lens?)

In the end, I'm excited to see what this baby can do.

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Well maybe. I think you might be giving Canon more praise for working a new optical variation of the classic double gauss than they deserve.

If the block diagram at the beginning of this thread is correct it looks like Canon have reused their lens design from the 1964 Canonet rangefinder camera ( " the poor man's Leica") that has a 45mm f/1.7 lens, and replaced one element with the aspherical one. If you go to the wiki page for Double Gauss lens that PBD linked to at the beginning of this thread you can see the Canonet block diagram at the bottom of the first diagram page.



Canon have given the first doublet a curved matting which is much more expensive to do than the straight bond in the 1964 lens, and this should give a more pleasant rendering. However my guess would still be that the lens is going to be sharper at the expense of rendering / bokeh. In other words it will chart well.

Sporgon said:

Well maybe. I think you might be giving Canon more praise for working a new optical variation of the classic double gauss than they deserve.

If the block diagram at the beginning of this thread is correct it looks like Canon have reused their lens design from the 1964 Canonet rangefinder camera ( " the poor man's Leica") that has a 45mm f/1.7 lens, and replaced one element with the aspherical one. If you go to the wiki page for Double Gauss lens that PBD linked to at the beginning of this thread you can see the Canonet block diagram at the bottom of the first diagram page.

View attachment 193747

Canon have given the first doublet a curved matting which is much more expensive to do than the straight bond in the 1964 lens, and this should give a more pleasant rendering. However my guess would still be that the lens is going to be sharper at the expense of rendering / bokeh. In other words it will chart well.

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Reposting the original for easy reference. (I actually had one of those old Canonet cameras, by the way). The differences are still pretty significant. I'm sure it will chart, the question is, will this dog hunt? We'll see in a few weeks.

jvillain said:

With IBIS now becoming a thing in Canon land that will dampen some of the demand for IS in the lenses.

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True, but they put IS in the 35mm and 85mm. Granted, those were released before a body with IBIS, but this just leads to the question of why they decided to release low to mid-price 35mm and 85mm lenses before the 50mm.

I'm cautiously optimistic about what this lens will be. I really hope that it's a star, Leica have shown that you can make a simple 50mm double gauss design absolutely stellar. Not that I'm expecting a summicron, but the fact that it's a double gauss design doesn't put me off in the slightest.

Antono Refa said:

I'm far from being an expert, but shouldn't it be the aperture, rather than the center of the lens elements?



My impression was the additional glass would not be needed for the FL range between RF's 20mm and EF's 44mm.

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FL is from the optical center of the lens to the optical center.

They cover it quite well here: https://photographylife.com/what-is-focal-length-in-photography#definition-of-focal-length

And just as they imply in there, things can get complicated real fast once you dive into the physics of it all. Simply based on this explanation you can see why lenses end up being what they are. The flange distance directly contributes to the distance of the optical center vs the sensor/film plane.

My point about additional glass had to do with WA lenses. A 14 mm lens is already by definition further in mm regarding its optical center compared to the optical plane. And thus additional glass is required to shift that projection. That is why WA lenses tended to be huge on DSLRs. With smaller flange distances less glass is needed to shift this focal point.

50s and 40s typically were relatively small on DLSRs due to the flange distance and lens FL. But for MILC with the flange being further back you end up with a longer lens. So when people talk as if the 50 mm lenses aren't taking advantage of the shorter flange distance they simply don't know what they are talking about.

gruhl28 said:

True, but they put IS in the 35mm and 85mm. Granted, those were released before a body with IBIS, but this just leads to the question of why they decided to release low to mid-price 35mm and 85mm lenses before the 50mm.

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Probably because a significant percentage of upgraders already have an EF 50mm of one kind or another (I have four: 50mm f/1.8II, 50mm f/2.5 macro, Yongnuo 50mm 1.4 and the EF 50mm f/1.2L), and even with the EF-RF adaptor it's still a lightweight small combination.

Moving this to RF makes sense now if it's cheap enough most RF mount users will upgrade.

Sporgon said:

Do designs that have worked well in the past still meet the demands and expectations required to be considered as working well to day ?

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I'm using on a regular basis a 1969 Leica M 50mm f2 Summicron.
Sharpness and contrast (edge to edge !!!) are still outstanding, even on EOS R cameras, and , for closeups, on high MP EOS DSLRs.
So: a BIG, AN ENORMOUS YES

WoodyWindy said:

(how many folks have inverted a 50 f1.8 to create an "instant" macro lens?)

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My old Rollei SL66 (kind of a Hasselblad but with bellows) could mount the 80/2 backwards for macro.