50 Summilux-M ASPH - OOF / Bokeh Balls - Is this normal?

[evikne]

Advertisement (gone after registration)

17 minutes ago, lct said:

No idea sorry but you may wish to ask our colleague luigi bertolotti who knows a lot about this lens.

Thanks, I can make a try:

@luigi bertolotti if you read this, do you know who was involved in the last redesign of the Summilux-M 50/1.4 (11868) in 1994?

[otto.f]

.

Edited February 10, 2020 by otto.f

[derleicaman]

This may help, as I do a comparison to many different 50mm lenses in my article "Bokeh Kings". It originally appeared in the LHSA Viewfinder.

https://www.reddotforum.com/content/2014/10/bokeh-kings/

FYI, the comparison between the 50/1.4 non-ASPH and 50/1.4 ASPH appear next to each other at f/1.4 and f/2.8. You can clearly see the smoother bokeh balls at f/2.8 on the original 50/1.4 Summilux

[wizard]

vor 20 Stunden schrieb lct:

This lens in question was the third generation of this SUMMILUX lens and was totally redesigned, optical and mechanical. E.g. The close-up focus was now 70 cm. and it had an telescopic lens hood.  

While I am not Luigi, I may be able to shed some light on this issue. From the above quoted English language text, you can clearly see that it was a German native speaker giving this information. In German, however, "optical" can mean both the optical design of a lens as well as the optical appearance of a lens, that is, its outer appearance.

Judging from the further information given in LCT's quote, it would appear to me that the mechanical redesign refers to the improved near focus limit (70 cm instead of 1 m), whereas the "optical" redesign refers to the fact that the then new version of that lens had a telescopic lens hood, which in fact did visibly alter the outer "optical" appearance of the lens versus the previous version.

Leica never communicated a complete redesign of the optical system of the pre-asph Summilux 1.4/50mm (except, of course, for the original redesign in the early sixties), and the lenses' cross-sectional representation included in the pdf lens description that was available from Leica until the end of production of that lens did not show any visible changes in the shape or arrangement of the lens elements either. Rather, the cross-sectional representation of the pre-asph Summilux 50mm stayed the same from its original redesign to the end of production. And while I am pretty sure that some slight redesign of the optical system will have taken place during its long production time, e.g. to accommodate for new lead free glass etc., I am also pretty sure that there was no major redesign at any point. In any event, if some kind of optical recomputation took place in the nineties, it would have likely involved Lothar Kölsch, as he was head of Leica's optical department at the time, if I remember correctly.

Cheers,

Andy

Edited February 10, 2020 by wizard
typo corrected

[lct]

I have those drawings on my HD but i don't recall where they come from.

Welcome, dear visitor! As registered member you'd see an image here…

Simply register for free here – We are always happy to welcome new members!

[wizard]

Hard to tell whether the slight variations that seem to appear from the above two lens sections are in fact the result of a recomputation or not. The different edges of some of the lens elements likely result from mechanical changes within the lens and affect the way certain lens elements are mounted in the lens, but should be optically insignificant. Surely, the general optical formula is very similar, if not the same, as evidenced by the almost identical lens spacings and curvatures. The slight differences that do seem to exist may be the result of some kind of recomputation to account for different glass types Leica may have been forced to use due to non-availability of the previously used glass types.

Looking at this question from another angle, assuming a major optical redesign of the Summilux 50 did in fact take place in the early nineties, I would be very surprised if Leica would not have officially communicated that optical redesign, if only to increase sales of this newly computed lens. There is no apparent reason for Leica to hold back on this, and they normally do communicate such optical redesigns (see for example the various versions of the Summilux 35 asph as well as the rather small redesign of the Summicron 35 asph, etc.).

The only reason for not communicating an optical redesign I can think of is that Leica was for some reason forced to use due new glass types, and therefore recomputed the lens based on the original optical formula without however achieving any noteworthy optical progress (if any at all). That would coincide with user experience, as I am personally not aware of any significant improvements in lens performance between, say, a 1984 copy and a year 2000 copy of that lens.

[lct]

Advertisement (gone after registration)

I have this brochure too:

LeicaM_5014_11868_broch_fr_roc.pdf

[wizard]

vor 10 Minuten schrieb lct:

I have this brochure too:

Interesting. Leica does admit 

Depuis son lancement en 1959, l'optique du SUMMILUX-M 1:1,4/50 mm a été recalculée plusieurs fois, ...

that this lens has been recomputed several times since its launch in 1959, but there is no mention in the brochure that the lens was (again) recomputed for the version which was presented at Photokina 1994. I am pretty sure that Leica would have indicated this in the brochure, as they do discuss all the other changes to the lens relative to the previous version in great detail.

 

[lct]

How do you understand « 7 lentilles dont 2 groupes accolés »? Could this apply to the v2's design as well? Just curious.

[Exodies]

Knowing nothing about lens manufacture - maybe they recomputed the design due to new software?

[wizard]

vor 17 Minuten schrieb lct:

How do you understand « 7 lentilles dont 2 groupes accolés »? Could this apply to the v2's design as well?

This refers to the two cemented groups each composed of two lens elements (the two lens groups on the right hand side of the above representations). And yes, this does apply to both v2 and v3, as both designs feature those two cemented lens groups. In German language, the optical construction of this Summilux 50 would be referred to as "7 Linsen in 5 Gruppen" (7 lens elements in 5 groups), as three of the lens elements are single elements, thus each constituting a group of its own, whereas the remaining groups are each formed by cementing (glueing) two lens elements together.

[wizard]

vor 20 Minuten schrieb Exodies:

Knowing nothing about lens manufacture - maybe they recomputed the design due to new software?

Lens computing software has certainly evolved over the years, as has the computing power of the associated hadware, but I doubt that they will recompute any existing lens just because new software or better computers are available. However, whenever a new computation is necessary (for some reason or another), they may well take advantage of better computers and better software.