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Jonathan Hanson

Confused about modern lens size/speed

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Can someone explain this to me? I just saw the release below of a new 50mm F2 full-frame Leica lens (at a suitably bonkers price). It's touted both for its speed and "compactness."

But 30 years ago, when I was shooting film with Canon F1s, a "fast" high-quality 50mm was 1.4, not 2, and half the length of this one. What gives?

 

Edited by Jonathan Hanson

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Lenses can be good, small, cheap or fast, but not all of it at the same time. Modern lenses, especially Leica, Zeiss and Sigma are traveling the same road, are spectacularly good, fast, but size and price fall by the wayside. To be fair, on a mirrorless camera there are no real size limitations like on a rangefinder camera for instance; balance is more important.

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It's senseless to try to encapsulate the differences in lens design due to requirements from thirty year ago film cameras to current state of the art digital camera lenses in anything less than a treatise of several dozen pages, if you're looking for real understanding of why things are the way they are. 

That said, from a simple practical point of view, this new lens is built into a system of excellent SL primes that all use nearly the same lens mount body such that they are all within just a few mm of each other, all produce absolutely wonderful performance and superbly consistent feel and ergonomics on the camera for which they are intended ... which is most definitely NOT a thirty year old SLR film camera in any way, and operates at a far far higher performance spec (and meets a far far higher set of expectations as well). It is a compact and super performing lens in this context. 

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I think the demands on a lens today far exceeds what it was 30 years ago. I did a lot of photography with my 35 Canada Summilux, but it had drawbacks under f2.8 it wasn't that sharp, which is totally unacceptable now. Lens design has changed and bigger lenses are the outcome. Still loved the size of the 35 Canada 'lux, here on a CL.

 

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I understand that lenses are far better than they used to be, but I still don't understand why they have to be so much larger (longer) to cover the same image circle. Moving down to APS-C, the 35mm Summilux for the CL is huge, although at least it is fast. I guess it will remain a mystery for now without the multi-page engineering treatise Ramarren alluded to . . .

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36 minutes ago, Jonathan Hanson said:

I understand that lenses are far better than they used to be, but I still don't understand why they have to be so much larger (longer) to cover the same image circle. Moving down to APS-C, the 35mm Summilux for the CL is huge, although at least it is fast. I guess it will remain a mystery for now without the multi-page engineering treatise Ramarren alluded to . . .

Well, think of two things right off the bat: 

  • The SL (and CL) have a shorter lens register than the Leica M, and much, much shorter than any SLR. It's on the order of 19mm, rather than 28 or 45mm. So the lens itself HAS to be longer to put the lens' nodal point in the right place. 
  • The major difference between the film recording medium and a digital sensor, is that the latter is very sensitive to the angle of incidence of the light hitting it where the former is extremely IN-sensitive to this same factor. So lens designs have to be construed for digital sensors in such a way that they allow the ray trace to hit the medium directly perpendicular for best performance. This complicates the lens design and required additional elements to implement. 

So there are reasons, many of which are not entirely obvious... These are just two factors in modern lens design that mean very significant differences. 

Edited by ramarren

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Incorporating auto-focus adds complexity, size and weight. In olden times, auto-focus was a distant dream.

Edited by wda

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A full set of TL Summicrons , 18, 35 and 50mm like the current 23mm, should provide a nice balance between speed and compactness - is full frame really necessary ?

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AF lenses are more or less bulky actually. My Nikkor ones are compact indeed (here a 50/1.4 compared to a 'Lux M) but they come from the last century and i don't know if the gigantism illness has spread to Nikon as well :rolleyes:

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56 minutes ago, lct said:

AF lenses are more or less bulky actually. My Nikkor ones are compact indeed (here a 50/1.4 compared to a 'Lux M) but they come from the last century and i don't know if the gigantism illness has spread to Nikon as well :rolleyes:

Nikon has is bad , really bad https://www.dpreview.com/articles/4416633505/cp-2019-finally-nikon-has-cut-a-z-noct-58mm-f0p95-in-half?slide=3

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If you want fast AF, you can't just add a motor to a manual focus design. For speed, that motor has to be able to move the lightest possible element for the shortest possible distance. That also means internal focusing, not just moving the whole body on a focusing mount. The lens has to be redesigned around it: I'm not a lens designer, but I could understand that this might mean bigger.

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10 hours ago, lct said:

AF lenses are more or less bulky actually. My Nikkor ones are compact indeed (here a 50/1.4 compared to a 'Lux M) but they come from the last century and i don't know if the gigantism illness has spread to Nikon as well :rolleyes:

Also, this Nikon lens doesn’t have an internal focusing motor if I am not mistaken. These days AF lenses all have internal focusing motors and must be made bigger.

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14 minutes ago, Tortuga said:

Also, this Nikon lens doesn’t have an internal focusing motor if I am not mistaken. [...]

True but the AFS version with "silent wave" motor is only 1cm taller if memory serves.

Edited by lct

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57 minutes ago, lct said:

True but the AFS version with "silent wave" motor is only 1cm taller if memory serves.

How big is the Nikon 50/1.8 S, which is a better comparison for size... 

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10 hours ago, lct said:

 

Not that bad for a f/0.95 lens. The current Nikon 35/1.8 is bulky but not as monstrous as some 35/2 i know of. 

http://j.mp/2z1PYGC

Formerly they had the restriction of the view/rangefinder. Now infinity is the limit.

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