50 Cron (latest) sharper than 50 Lux ASPH?

[otto.f]

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The one with the built-in hood is more flare-prone, latest version; my experience. Maybe it's just the shorter hood that causes this

 

Chrome versions are indeed built with smaller tolerances (according to Puts)

[01af]

Focus shift. [...] the Summicron shows very little focus shift, and the Summilux, which is more at risk because of the greater speed [...], solves the problem by means of its floating element.

It seems it's becoming a common misconception to believe that floating elements are there to address focus shift. They are not. Instead, they address all kinds of aberration (in particular, spherical) at focus distances shorter than infinity. Of course, by improving the overall level of correction, they also help reducing focus shift—but only indirectly so.

 

So, the Summilux-M 50 mm Asph doesn't solve (or actually, reduce) the problem of focus shift by means of floating elements but by means of an exceptionally high level of correction of spherical aberrations.

 

Regarding the original question ... according to the MTF curves published by Leica, the Summilux-M 50 Asph at f/1.4 is as good as or better than the Summicron-M 50 at f/2 across the better part of the frame, except the farthest corners. It's the same when both lenses get stopped down to f/2.8. So the Summicron sure is not sharper than the Summilux Asph generally. If it looks sharper in real-world pictures then most likely the Summilux wasn't properly focused.

 

For practical intents and purposes, all current Leica M 50 mm lenses are equally sharp, basically. Take your choice of a 50 mm lens after speed, size, weight, and cost, but not sharpness.

[lars_bergquist]

Lars,

 

May I ask where you have that information? In my limited experience, the opposite is true regarding the aspherical and focus shift.

 

Horea

 

In this very forum. You can't have missed it.

 

The old man

[lars_bergquist]

It seems it's becoming a common misconception to believe that floating elements are there to address focus shift. They are not. Instead, they address all kinds of aberration (in particular, spherical) at focus distances shorter than infinity. Of course, by improving the overall level of correction, they also help reducing focus shift—but only indirectly so.

 

So, the Summilux-M 50 mm Asph doesn't solve (or actually, reduce) the problem of focus shift by means of floating elements but by means of an exceptionally high level of correction of spherical aberrations.

 

But of course! A floating element by itself does not cure focus shift. It is there in order to give the lens designer more degrees of freedom to do what the designer thinks should be done – including reducing focus shift. There are other ways too to do that, more aspherical surfaces, more lens elements ... but both economic constraints and regard for bulk dictated floating elements.

 

Lens aberrations are never addressed one by one, and with one specific design item. For instance, you cannot say which lens element or whatever that "addresses" longitudinal chromatic aberration! A lens design is a package. But the more complicated the corrections get, the more degrees of freedom are needed. Without the floating element, no increased corrrection. Simple as that.

 

The old man from the Age of the Slipstick

[lars_bergquist]

Lars, was your flare-prone 50 Summicron the older one with separate hood, or the newer one with built-in hood?

 

(By the way, this "version" naming system gets a bit confusing because for some there is a version 4 and a version 5, and for others there are two different version 4's and no version 5.)

 

My lens was the v.4 first mount (tabbed, separate hood).

 

I agree, confusion reigns. I think "version" should be reserved for optical versions – and there should be a difference in optical design between the versions. A change in the mount only should not qualify. We are after all photographers, not stamp collectors.

 

The old man from the Age of Film

[Xmas]

Hi

 

The performance of the lenses may be different with Digital and film, i.e. the UV/IR wont help either lens, seen the latest coded cron (as new) iris image badly, you needed to remove the filter.

 

Both lenses are so good you will need a heavy tripod to see much difference f/5.6 of smaller, or brace against a post if you are real good.

 

Both lenses do suffer from veiling flare where the micro contast is compromised e.g. when there is a profile light, one may be better then other, not tried tests. Cooperator sold his kit...

 

Noel

[yanidel]

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According to Jean-Marie Sepulchre book on the M9 where he tested both lenses with DxO, the 50mm Cron is slightly sharper on center at F2.0. Yet, the Lux Asph is better starting at the thirds up to the very corners. From F4.0 to F8.0, performance is basically the same. Note that in terms of chromatic aberration, the Lux is significantly better.

[sm23221]

For practical intents and purposes, all current Leica M 50 mm lenses are equally sharp, basically. Take your choice of a 50 mm lens after speed, size, weight, and cost, but not sharpness.

 

I fully agree. In real world photo making all of my 50's (Nocti 0.95, Elmar, Cron) become indistinguishable at about f2.8 on up. If you were presented with an 8x10 print using each lens of a real-world image (not a brick wall) you will not be able to match the lens to the proper photo. Try it...

[pgk]

If you were presented with an 8x10 print using each lens of a real-world image (not a brick wall) you will not be able to match the lens to the proper photo. Try it...

I did this 30 years ago by MTF and real world comparisons of Leica M>Focotar vs. Minolta reflex>Minolta enlarging lens. Whilst the overall MTF data showed the Leica to be substantially better, 10" x 8" B&W prints showed virtually no difference. If you then looked at the relevant MTF data this was not surprising. So a similar 50mm M lens comparison is not going to show differences.

[otto.f]

Sharpness is not the criterium to decide, it's what you want with selective focus, shallow DOF. Some people don't see anything in that style, for instance Ansel Adams wanted everything sharp, period, and was totally devoted to tonal scale, but that was mainly landscape photography

[bocaburger]

.........claims about the unsatisfactoriness or "unrealness" of the MTF are just arm waving, attempts to explain why this or that favourite lens is really super even when measured performance is so-so.

 

Sure that happens, but in the case of the 50 Cron vs 50 Lux-ASPH, the MTF charts show the lenses are quite close in performance, and both on quite a high order. Compared to eg. 35 Lux vs 35 Lux-ASPH. Or even the 50 Lux vs Lux-ASPH. MTF charts are made with the lens fastened securely to test apparatus, with as many factors as possible held as close as possible to a standard. Photography is made with the lens fit to the owners' cameras, vulnerable to things like rangefinder adjustment and body-film/sensor tolerances. That's even before considering photographer-induced variables such as hand-holding (or even varying sturdiness of tripods), exposure, film/sensor characteristics, film development/digital post-processing, print size, and so on. The closer to each other the MTF values for 2 lenses fall, the more likely those foregoing real-world variables are going to render the differences moot, or even make them appear contrary to the MTF charts.

 

So in the case of these 2 lenses, I think there's a good chance people are seeing legitimately what they are reporting, despite the contradictory opinions.

[jaapv]

. MTF charts are made with the lens fastened securely to test apparatus, with as many factors as possible held as close as possible to a standard.

Actually, in most cases, including Leica lenses, MTF charts are computer-generated. Anyway, regarding the OP " sharp" and "sharper" are non-parameters in optics. We have things like resolution, contrast, micro-contrast, etc., but " sharpness" cannot be quantified, making the KR statement meaningless, as many of his statements are.

[farnz]

Isn't the matter logically settled by the argument that, according to its designer Peter Karbe, the 50 Summilux asph is actually an APO (apochromatic) lens whereas the 50 Summicron is not? According to Karbe the 50 Summilux asph has an identical design to the 75 APO-Summicron asph but was never called an APO lens even though it, too, uses anomalous partial dispersion to correct for spherical aberration and chromatic dispersion to produce apochromatic performance.

 

An apochromatic lens will intrinsically be sharper than a non-APO lens because the red blue and green wavelengths focus in the same plane so the 'spot' must be smaller and the image therefore sharper.

 

Pete.

[lars_bergquist]

[ ... ]

So in the case of these 2 lenses, I think there's a good chance people are seeing legitimately what they are reporting, despite the contradictory opinions.

 

Dear Bocaburger – my remark was a general one, not addressed to the comparison of these two lenses. Under circumstances that do not test the 'cron's resistance to flare, they both deliver results from f:2 to 16 that are practically identical (and in any case, I do not advocate building mountains out of MTF molehills). The reliable anti-flare performance was the reason why I exchanged the first lens for the second; I cannot honestly say that I need the extra stop of speed. "Need" and "want" are two different things.

 

It is also a fact that different people "see" different things even when they look at the same thing. This is not only because we are different and act differently, but because our percptual apparatus is not as straightforward as people think. "I saw it with my own eyes" is a phrase that will draw a sceptical smile from any competent neurologist or perception psychologist – not to speak of an evolutionary psychologist.

 

The old man from the Age of Evidence

[lars_bergquist]

[ ... ]

An apochromatic lens will intrinsically be sharper than a non-APO lens because the red blue and green wavelengths focus in the same plane so the 'spot' must be smaller and the image therefore sharper.

 

Pete.

 

I looked up the published MTF curves. There are no published data for the 'lux at f:2, or for the 'cron at 1.4 (natch!) but as far as I can see, these two lenses run neck to neck f-stop by f-stop in the frequency modulation race. The impression of sharpness is very similar, and it is of course an acheivement for a 1.4 lens to perform like a 2 lens; but the 'lux is not "intrinsically sharper" than the 'cron.

 

But in order to acheive that rough parity, the 'lux must be a more advanced and complicated design than the straightforward old 'cron, a classical Gaussian layout. That includes advanced glass. That is the price of an extra f-stop.

 

Please note that "apochromatic" is a very slippery term. There is no norm or standard for applying it. The classical definition related to microscopes: A common point of focus for axial or paraxial rays of three colours. This would make most current Leica lenses "apos", but Leica's internal definition includes off axis performance so it is much more stringent. Anyway, it seems that Leica have decided to apply the apo designation quite sparingly, and only to lenses of longer focal length than 50mm.

 

The old man from the Age of Achromats

[Xmas]

Hi

 

Two points.

 

The cron uses the 1.9 refractive index glass used in the f/1 noct, (I think for four of its elements) this to allow a rationalised design, i.e. simpler and cheaper to make. And Apo correction is only easily detectable in long focus lenses when the normal blue and red color correction if not really sufficient, and you need to optimise for colors futher apart, (or three colors), it will have less effect in a 5cm lens. I dont think they mill the brass any different from the aluminium whatever Puts says, suprised if they even make two lens cells. And the designers would test all their prototypes on a MTF machine before asking a photog to try, they would do more MFT runs than normally published, & spot diagrams...

 

The best lens for performance is the f/2.5, in theory it is easier to make a slower lens, and they performs better in pactice. The /2.5 is more modern then the cron, so.

 

If you use the lens in normal situations its flare tolerance is critical, if you dont like/ want flare, the Planar ZM and cron, arn't as flare free as I'd like some of the time. This does not trouble me but I normally use a post 94 Elmar and for LTM a CV f/2.5. My cron is a '85 so should be multicoated.

 

Noel

[tgray]

I seem to recall having some flare issues with my last version 50 Summicron. When I say flare issues, I don't mean it ruined every shot, or even 5% of shots. But I do recall having a couple shots that were ruined by a flare when I thought they should have been fine. No where near as bad as the Canon EF 50/1.4 though. I should note that I didn't scan the offending shots, so it's a bit hard for me to verify this notion.

 

I've not had any problems with the ASPH Summilux. At this point in time, I've used the ASPH a lot more than and for longer than the Summicron.

 

That being said, I don't see where the ASPH gives up anything important to the Summicron. If it's not as sharp at f/2, it's by such a small amount that it doesn't matter to me. Your mileage may vary. If you need/want f/1.4, get the ASPH with no worries. If you don't, get the Summicron, the Summarit, the Elmar, the Planar...

 

For the record, I think the ASPH has a smoother bokeh than the pre-ASPH. Not that the pre-ASPH is bad; it can be pretty interesting at times. I'm tempted to get one, but I know that would be a waste to have both. I think I'd rather have and Elmar to pair up with the Summilux.

[otto.f]

[quote name=tgray;1691494

For the record' date=' I think the ASPH has a smoother bokeh than the pre-ASPH. [/quote]

 

That is a special view, and therefore worth recording, I had the impression that most people see it the other way around

[ho_co]

Isn't the matter logically settled by the argument that, according to its designer Peter Karbe, the 50 Summilux asph is actually an APO (apochromatic) lens whereas the 50 Summicron is not? ...

Pete, to my knowledge, there was a single report of his having said that, which AFAIK Dr Karbe hasn't repeated in writing. Erwin Puts says 50/1.4 ASPH is definitely not an apochromat. See http://www.imx.nl/photo/leica/lenses/lenses/page57.html:

The color correction is excellent, but not of APO calibre. Some red and green color fringing can be detected at high magnifications.

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Hallo,

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[ho_co]

May I ask where you have that information? In my limited experience, the opposite is true regarding the aspherical and focus shift.

 

Horosu, see http://www.l-camera-forum.com/leica-forum/digital-forum/17699-very-interesting-answer-leica-35mm-1-a.html. It was a very wrenching discovery for many of us, as shown by the sheer number (427) of posts in the thread.

 

Following that, there was a long article in LFI which went over focus shift with particular interest in the 35/1.4 ASPH, where Leica said something to the effect that "if we were designing it today, we'd give it a floating element."

 

And then a year or so later, the current 35/1.4 ASPH appeared, with all elements and surfaces identical to those of its predecessor (according to Erwin Puts), but with the floating group.

 

No disagreement with Olaf and Lars on the fact that a floating element allows a lot of corrections. In this case, the new lens shows minimal focus shift, improved close-up performance, and improved contrast. Some of that is certainly achieved by the new mount, but the only optical change is the addition of the floating group.