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Lens design. Specifically 35/1.4 and 24/1.4.

  
 
wolfloid
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p.1 #1 · p.1 #1 · Lens design. Specifically 35/1.4 and 24/1.4.


I hope that at least some among you may be able to add some input. I have and use the Leica Summilux 35/1.4, and although it’s not the smallest of lenses, it’s small enough for me to love using it, and needless to say it’s image quality is excellent. I would like the same in 24 mm. When I look at Leica Lenses, the Summilux 24/1.4 is considerably larger than the 35. This is not the case with Sony’s GM lenses, in gact it is the reverse.

Is there an obvious reason for this? Could Leica make a 24 mm 1.4 lens as small as the 35 and just as high quality?



Nov 17, 2023 at 10:45 AM
BastianK
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p.1 #2 · p.1 #2 · Lens design. Specifically 35/1.4 and 24/1.4.


Not really.
In absolute terms the Sony 24mm 1.4 GM is also much bigger than either of the Leica lenses you mention.

Designing such lenses for the Sony system is much easier: no need to use up space for the rangefinder coupling,
shorter back focus distance and a generally bigger lens mount to open up design freedom.

When you look at the diagrams of the Sony lenses you will notice that they have pretty big rear elements close to the sensor,
this is physically not possible for M-mount lenses.

This is also part of the reason why Sony's GM 24mm 1.4 and 35mm 1.4 offer way better image quality and nicer bokeh than the Leica M equivalents.



Nov 17, 2023 at 02:04 PM
RustyRus
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p.1 #3 · p.1 #3 · Lens design. Specifically 35/1.4 and 24/1.4.


Have you put the 24 1.4 Lux in your hands?

It’s really not that big- My only complaint is it can’t take normal filters-

Beautiful lens IMO






Nov 17, 2023 at 02:15 PM
wolfloid
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p.1 #4 · p.1 #4 · Lens design. Specifically 35/1.4 and 24/1.4.


„Designing such lenses for the Sony system is much easier: no need to use up space for the rangefinder coupling,“

I wasn‘t asking why sony lenses are larger, but why for the Sony the 24/1.4 is smaller than the 35/1.4, whereas in the M system the 24/1.4 is much bigger than the 35/1.4. That is what puzzles me.



Nov 18, 2023 at 05:18 AM
BastianK
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p.1 #5 · p.1 #5 · Lens design. Specifically 35/1.4 and 24/1.4.


As I already said it is generally harder to design high performing fast wide angle lenses for M-mount.
For a fast 24mm the advantage of designing it for E-mount is bigger than for 35mm, therefore in the Sony world a 24mm 1.4 can be smaller than a 35mm 1.4 of similar performance.



Nov 18, 2023 at 06:47 AM
Nushi
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p.1 #6 · p.1 #6 · Lens design. Specifically 35/1.4 and 24/1.4.


BastianK wrote:
As I already said it is generally harder to design high performing fast wide angle lenses for M-mount.
For a fast 24mm the advantage of designing it for E-mount is bigger than for 35mm, therefore in the Sony world a 24mm 1.4 can be smaller than a 35mm 1.4 of similar performance.


I think you're likely mostly wrong. Even if the mount and flange distance has some impact it's more likely that the Sony 35 is much less optimized for size than the Leica 35. When the envelope of the 35 is relaxed it's much easier to design a 24 of similar size.



Nov 18, 2023 at 08:50 AM
BastianK
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p.1 #7 · p.1 #7 · Lens design. Specifically 35/1.4 and 24/1.4.


Nushi wrote:
I think you're likely mostly wrong. Even if the mount and flange distance has some impact it's more likely that the Sony 35 is much less optimized for size than the Leica 35. When the envelope of the 35 is relaxed it's much easier to design a 24 of similar size.

I am curious to see some proof for your theory.
I know of several 35mm 1.4 lenses made out of only 7 elements.
I do not know a single 24mm 1.4 with less than 10.

I would also like to know why Sony should make their 35mm 1.4 bigger than necessary,
when their recent lenses are already always smaller and lighter than the comparable Canon and Nikon alternatives.
And no, price is not the answer. I would be greatly surprised if all the special glass elements of the Sony 35mm 1.4 were cheaper to produce than those in the Leica 35mm 1.4 FLE.



Nov 18, 2023 at 09:08 AM
Nushi
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p.1 #8 · p.1 #8 · Lens design. Specifically 35/1.4 and 24/1.4.


BastianK wrote:
I am curious to see some proof for your theory.

Proof is almost impossible because any lens is made with a different set of compromises, by different manufacturer at different times. It's really difficult to fully grasp the impact of mount and flange distance because all the tech around is moving simultaneously. Software corrections, available materials, manufacturing technology and not the least profit. Even seeing the impact compared to dslr's is difficult because dslr lenses are barely designed anymore (Pentax is not enough of a sample size. Loxia 21 f2.8 and Pentax 21 f2.4 are about the same size.)

BastianK wrote:
I know of several 35mm 1.4 lenses made out of only 7 elements.
I do not know a single 24mm 1.4 with less than 10.


That's my main argument. Curious that you see it as evidence of the opposite.

The GM 35 has like 14 elements right? It's perfectly doable to make a good fast 24 within than envelope. Element count is obviously not the end all but a good proxy.

BastianK wrote:
I would also like to know why Sony should make their 35mm 1.4 bigger than necessary,


Well one way to look at it would be to note that the Sony 35 and 24 are a *lot* larger than the Leica equivalents. Now if the Sony has significant advantages due to flange and mount you may reasonably conclude that the Sonys are larger than necessary. Naturally the performance differs and some may find the Leica performance unacceptable which changes the equation.

Necessary is defined by product vision and a multitude of compromises. The GM's aren't produced for rangefinder cameras and come from a different product "culture" where a larger size lens is more acceptable. I'm sure they put the extra size to use reducing aberrations, creating a look or saving on manufacturing cost. I don't think a GM sized 35mm f1.4 would fly on Leica M.









Nov 18, 2023 at 10:02 AM
nehemiahphoto
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p.1 #9 · p.1 #9 · Lens design. Specifically 35/1.4 and 24/1.4.


BastianK wrote:
Not really.
In absolute terms the Sony 24mm 1.4 GM is also much bigger than either of the Leica lenses you mention.

Designing such lenses for the Sony system is much easier: no need to use up space for the rangefinder coupling,
shorter back focus distance and a generally bigger lens mount to open up design freedom.

When you look at the diagrams of the Sony lenses you will notice that they have pretty big rear elements close to the sensor,
this is physically not possible for M-mount lenses.

This is also part of the reason why Sony's GM 24mm 1.4 and 35mm 1.4 offer way
...Show more

This. And when I took apart a busted RX1 years ago, the rear element is large and plastered on top of the sensor.



Nov 18, 2023 at 04:58 PM
Olaf G
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p.1 #10 · p.1 #10 · Lens design. Specifically 35/1.4 and 24/1.4.


Nushi wrote:
I think you're likely mostly wrong. Even if the mount and flange distance has some impact it's more likely that the Sony 35 is much less optimized for size than the Leica 35. When the envelope of the 35 is relaxed it's much easier to design a 24 of similar size.


IMHO the flange distance plays an important role here.
It is 27.8 mm for Leica M. The Lux 24 needs to be a bulky retrofocus design while the Lux 35 does not necessarily needs to be a retrofocus design due to it's longer focal length.
The flange distance for Sony is 20 mm, so basically Sony does not need to apply different design principles to either of the two lenses. However, due to the bigger sensor stack and its sensitivity to the ray angles they are most likely both retrofocus designs. That makes them both bulky (well, they have autofocus too) in comparison to the Lux 35, but the 24mm is smaller than the 35mm.




Nov 19, 2023 at 03:22 AM
 


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Nushi
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p.1 #11 · p.1 #11 · Lens design. Specifically 35/1.4 and 24/1.4.


Olaf G wrote:
IMHO the flange distance plays an important role here.
It is 27.8 mm for Leica M. The Lux 24 needs to be a bulky retrofocus design while the Lux 35 does not necessarily needs to be a retrofocus design due to it's longer focal length.
The flange distance for Sony is 20 mm, so basically Sony does not need to apply different design principles to either of the two lenses. However, due to the bigger sensor stack and its sensitivity to the ray angles they are most likely both retrofocus designs. That makes them both bulky (well, they have autofocus too)
...Show more

Hang on aren't you basically saying that the flange distance doesn't matter because in practice the sensor stack puts limitations on the design? Which was pretty much my argument, other factors beyond mount and flange seem to be more important in the end.

I'm not skilled enough to read block diagrams and was looking for ray tracing of all four lenses but couldn't find them all. If anyone find them it would be interesting. https://opticexplorer.sharedigm.com/#search?query=summilux has some of the lenses.

As I said I can't really read block diagrams with certainty but are we sure the current 35 lux isn't a retro focus design? https://leica-camera.com/sites/default/files/pm-82885-EN_Datenblatt%20Summilux%2035%20-%202022.pdf



Nov 19, 2023 at 05:07 AM
Olaf G
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p.1 #12 · p.1 #12 · Lens design. Specifically 35/1.4 and 24/1.4.


Nushi wrote:
Hang on aren't you basically saying that the flange distance doesn't matter because in practice the sensor stack puts limitations on the design?


Yes, this might be true for the Sony. AFAIK, the Leica does have a thinner sensor stack that makes it better suitable for lenses that are less retrofocus in design as long as the mount allows for it.




Nov 19, 2023 at 06:58 AM
wolfloid
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p.1 #13 · p.1 #13 · Lens design. Specifically 35/1.4 and 24/1.4.


IMHO the flange distance plays an important role here. It is 27.8 mm for Leica M. The Lux 24 needs to be a bulky retrofocus design while the Lux 35 does not necessarily needs to be a retrofocus design due to it's longer focal length. The flange distance for Sony is 20 mm, so basically Sony does not need to apply different design principles to either of the two lenses. However, due to the bigger sensor stack and its sensitivity to the ray angles they are most likely both retrofocus designs. That makes them both bulky (well, they have autofocus too)...Show more

That explanation seems to be most on point. Thanks for that!



Nov 19, 2023 at 11:39 AM
Nushi
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p.1 #14 · p.1 #14 · Lens design. Specifically 35/1.4 and 24/1.4.


Olaf G wrote:
the Lux 35 does not necessarily needs to be a retrofocus design due to it's longer focal length.


This thing about the 35 lux being retrofocal or not is interesting to me. The Zeiss 35 mm f1.4 distagon is obviously a ... distagon ie retrofocal design. Looking at the lens structure the current 35 lux it's very similar to the 35 distagon. It's smaller though so perhaps a non bulky retrofocal design.

If the current 35 lux is a "distagon" design it suggests that the Leica sensor stack also benefits from retrofocal designs for focal lenghts longer than flange distance despite all the effort they've put it to limit the issues.
















Nov 20, 2023 at 02:08 PM
Olaf G
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p.1 #15 · p.1 #15 · Lens design. Specifically 35/1.4 and 24/1.4.


Nushi wrote:
This thing about the 35 lux being retrofocal or not is interesting to me. The Zeiss 35 mm f1.4 distagon is obviously a ... distagon ie retrofocal design. Looking at the lens structure the current 35 lux it's very similar to the 35 distagon. It's smaller though so perhaps a non bulky retrofocal design.

If the current 35 lux is a "distagon" design it suggests that the Leica sensor stack also benefits from retrofocal designs for focal lenghts longer than flange distance despite all the effort they've put it to limit the issues.



https://i.imgur.com/wuZiSZL.png">






Well, without the aspherical element the 35 Lux looks almost symmetrical to me...



Nov 20, 2023 at 04:58 PM
Geoff CB
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p.1 #16 · p.1 #16 · Lens design. Specifically 35/1.4 and 24/1.4.


wolfloid wrote:
„Designing such lenses for the Sony system is much easier: no need to use up space for the rangefinder coupling,“

I wasn‘t asking why sony lenses are larger, but why for the Sony the 24/1.4 is smaller than the 35/1.4, whereas in the M system the 24/1.4 is much bigger than the 35/1.4. That is what puzzles me.


Because the 35mm 1.4 is one of Sony's first designs for the mount and they've gotten better a lens design since then, prioritizing size.

All lens design is compromise. You can have a Tiny 50mm 1.4 with optical imperfections or a massive one that's perfect. The wider you go, the more difficult it is to make the lens fast as well as well corrected in the corners. Everything is a balancing act.



Nov 21, 2023 at 05:19 AM
wolfloid
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p.1 #17 · p.1 #17 · Lens design. Specifically 35/1.4 and 24/1.4.


Because the 35mm 1.4 is one of Sony's first designs for the mount and they've gotten better a lens design since then, prioritizing size.

Isn’t the 35/1.4 GM one of Sony’s most recent and perfected designs, and the smallest 35/1.4 on any mirrorless system? It was that that made me wonder how they managed to shrink the 24/1.4 so far.



Nov 21, 2023 at 06:50 AM
RustyBug
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p.1 #18 · p.1 #18 · Lens design. Specifically 35/1.4 and 24/1.4.


The wider you go, the tougher it gets.
Thngs like vignetting, distortion, CA, etc. become more challenging to control as the angles of incidence change.

I'm not versed in Sony, but ... there are two main things that come to mind, and a few others that follow.

#1 the Sony mount is in fact larger, and this changes the angles of incidence that the designers have to work with. I understand your question isn't Sony vs. Leica, rather Sony vs. Sony and Leica vs. Leica, at why not a parallel size relationship in each brand.

#2 the level of correction(s) and the methods of design used to achieve them vary. I think it would be interesting to see the lens diagram for ALL FOUR lenses to assess if Sony retained the SAME approach in both their 35 and 24. Also, if Leica retained the SAME approach for their 35 and 24.

It was mentioned that Sony "got better" and the 35 was an early design. IF (I'm not versed in Sony) that is true that Sony used DIFFERENT designs between the 35 and 24, while Leica used similar designs to retain consistency between the drawing style of their 35 and 24, then that could vary well be your differential for the non-sequitur aspect that Leica got larger (following the "wider you go, the tougher it gets" paradigm, for ceteris paribus), while Sony managed to get smaller.

The 'assumption' being that BOTH Sony and Leica remained consistent within their lens design pairing. Until we see the lens diagrams for the four lenses, we cannot make that assumption for BOTH Sony and Leica as to whether the retained the consistency between their 35 and 24 counterparts ... or, if they deployed a different approach between the pairings.

NOW, as to whether or not Leica CAN make a smaller 24/1.4 that is smaller than their 35 counterpart ... certainly they can. But, the question becomes at what expense in the quid pro quo to do so.

Different drawing style, breaking consistency from the 35 Lux
More vignetting
More distortion
More CA

One point about distortion ... designing with simple distortion vs. designing with complex (mustache) distortion affords different approach opportunities, too.

Without seeing the lens diagrams of all four ... we will continue to be guessing. But, a quick guess on my part is that Sony did NOT use the same design approach for their 24 as their 35. Then, the following question is what also changed in drawing style, vignetting, distortion, CA, etc. as a result of that. Because, in order to retain ceteris paribus of a 35 and 24, the 24 would need to be larger, or would incur more aberrations. So, that brings the point of how much OPTICAL correction did Sony forego in the 24, and did they design the 24 with the allowance for COMPUTATION correction, instead of OPTICAL correction. Meanwhile did Leica retain similar drawing style and OPTICAL correction levels. I don't have the answers, but these would be (some) of my questions in quest of your search for the rationale as to the difference of why Sony did it, but Leica did not.

Again, I'm not versed in Sony, but these are aspects that I'd seek to know. The question regarding the non-sequitur relationship is based on the assumption of ceteris paribus between the 35 and 24 pairings. But, I'd venture that the ceteris paribus of Leica is more closely aligned than that of the Sony pairings. Again, we need to see the lens diagrams of all four to understand how much ceteris paribus is actually retained, vs. departed from.

Then, we'd need to see the comparative results of the optical projections of all four lenses, to see where the quid pro quo may have occurred that allowed for the smaller physical size of the Sony 24 from its 35 brethren.

Without the lens diagrams and the MTF's, distortion, vignetting, CA performance information ... to verify or refute the assumptive nature of non-sequitur vs. ceteris paribus, we are left to a speculative conjecture.

Hopefully someone will post up the optical information (of all four) needed to draw better determinations, or better illustrate the difference(s) that will unfold to answer your question.

Short answer ... something is different between the Sony 35 / 24 more so than Leica retaining more of the same between their 35 / 24 is my guess.

One other thing that comes to mind ... since the f/1.4 is based on central measurement, T-stops would be interesting to note for the four lenses (pairings) as well.




Nov 21, 2023 at 07:16 AM
wolfloid
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p.1 #19 · p.1 #19 · Lens design. Specifically 35/1.4 and 24/1.4.


I understand your question isn't Sony vs. Leica, rather Sony vs. Sony and Leica vs. Leica, at why not a parallel size relationship in each brand.

Absolutely, exactly that.

This is what I understand - and I am far from being a lens expert.

1. The Sony 24mm 1.4 GM was the first of the Sony GM primes introduced, and was hailed as a marvel of resolution, image quality, and compactness - the best AF mirrorless lens on the market (maybe best of all 24mm f1.4 lenses available).

2. Then came the 35mm f1.4 GM, about 2 years ago. Hailed on this site, on Phillip Reeve, and on many other sites as the most perfect of all 35mm f1.4s, and universally claimed as sharper centrally, in midfield and in the corners, with much smoother bokeh than any of the M 35mm f1.4 Summiluxes, and even better than the M Zeiss 35mm f 1.4.

3. So both Sony GM lenses seem to be peak performers, both are the smallest and lightest in their class of mirrorless AF lenses. Given how much newer the designs are, and Sony’s ambitions, their excellence, and their more compact size is not so surprising.

The only thing that surprises me is that the 24mm GM is smaller and lighter than the newer 35mm GM, whereas in the Summiluxes it is so markedly the other way around.

As Rusty bug implies, there is almost certainly some design decision/constraint that necessitated the extra size (though still not so big) of the 35 GM.

Maybe there is something in the retrofocus/symmetrical design differences in the Summiluxes, but perhaps, as has been mentioned, without the lens diagrams for all the lenses (interpreted by someone who can read them) the conundrum is difficult to solve.

Thanks for all the input though.





Nov 21, 2023 at 12:34 PM
Maknof
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p.1 #20 · p.1 #20 · Lens design. Specifically 35/1.4 and 24/1.4.


Design are easy to calculate but they are made not only with optical feature in mind.
Sony lenses are autofocus, af must be fast, using silent motors, with low torque and low consumption.
So minimal movement of one or at most two lenses.
You have to find space for than motors and get a telecentric design.
Hard to achieve with symmetric or classic design.
Leica use a brass elycoid, they can chose to move one lenses, all lenses, a block of lenses without worry about torque or speed.
Movements are done through threaded pipes.

Then you have to manufacture that lenses, with some number of production in mind, a cost and an expected revenue, a factory that make an autofocus lens need different equipment, a different number of worker, with different skillset compared to a factory that make a manual focus lens.

SL lenses, are not miniaturization masterwork and ate more similar to sony lenses than m-mount lenses.



Nov 21, 2023 at 03:53 PM
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