If I may just offer my experience ...
I have the 110XL. Soon after I bought it I had focussing issues. Real weird issues. This was maybe 8 years ago or so. It turned out that Schneider had used a poor cement between two elements. I had to ship it to California (from Australia). Schneider were very reasonable about it all.
I reckon the 210XL could suffer a similar fate given that it will come from the same factory floor.
Be careful.
With wrong spacing you will always get a sharp picture in the center (by refocusing).
But there will be growing field curvature and unsharpness to the borders of IC which you cannot minimize by refocusing but only by closing the aperture.
Symmetrical lens constructions like Symmar, Ronar, Claron and even Super-Angulon are not critical to small spacing errors. Super Symmar XL is a extremly unsymmetrcal lens construction, and this is why Schneider warned against incorrect mounting.
If you want to test your lens to spacing error, compare the border resolution at given centerfocus and opened aperture within various spacings by screwing rear lens.
Last edited by rawitz; 6-Apr-2024 at 07:49.
Very interesting point about symmetrical vs asymmetrical optics.
Have not read thru entire thread so maybe this has been answered...but if I were to want my 110XL tested for alignment - to whom might I send it?
(as I've said previously...I'll be hanging on to my 120 SA no matter what!)
There is another potential cause of focus issues, I'm not sure if Schneider had trouble, in this era, but I know that Leica did, with the first aspheric M 35/1.4Originally Posted by swmcl
The XL's use an aspheric surface. Getting the required surface quality ( 'figure error' ) is harder on an asphere than a spherical surface. Whether the lens is directly ground and polished, or a moulding ( the mould still has to be ground and polished ) , there can be errors taking the form of concentric ripples , present in the finished surface. There can also be a central peak or dip in the surface ( I am talking about errors only at the 1µm level ) .
The ripple is the main cause of 'onion ring bokeh' that is discussed a lot on the digital forums with fast 35mm lenses.
The central peak or dip is a problem in other ways . It can cause a significant stop-down focus shift - like that seen on early lenses in the 19th & early 20th century which were poorly corrected for spherical aberration. I think Leica had this problem.
To be clear, I do not know if this affected any Schneider XL's, but I know that we in the Avionics and Infra-Red fields saw both types of problems in lenses in the late 90's and early 2000's, which gradually went away as we improved measurements and procedures, and the machines got better.
The flawed cementing issue was said to be related only to the earlier serial numbers of the 80 XL and 110 XL, not the 210XL. Schneider replaced them for free only up to a certain cut-off date; so some flawed one are still out there. That affected serial number list should still be available from Schneider, or perhaps someone has reposted it.
Lenses of this price and quality, and limited availability, no doubt had the aspheric element quality control figured out. That never was in question with end users, just the experimental new sealant. In my neighborhood, contract aspherics have been turning out flawlessly for decades. I personally interacted with them in terms of facilities supplies as far back as the late 70's. The tooling was perfected quite awhile ago, then got even better, and led to higher quantity capacity as well. But their customers have huge Govt budgets and need it done right every single time.
Lenses of the price and quality of the Summilux-M 35 Aspheric didn't, at the start.
Of course it's not fair to compare the capabilities of a price-is-no-object custom contractor which has specialized in high-end aspherics for decades with consumer optics, even from Leica, which is bargain basement priced by comparison. And I of course don't know exactly how Schneider's Symmar XL elements were made, only that there seem to be no complaints over this series of lenses, and only praises about their exceptional performance, with the exception of the early sealant failure issue.
1. Nobody made this comparison, who are you talking about ?
2. It was cement that was discussed, not sealant.
However I'm happy to hear and accept that the majority of the XL lenses were great.
But I accept the
Hi again, Mark. I'm obviously not an engineer myself. But as a materials provider, I interacted with the owner of Tinsley Labs several times a week, probably the most advanced maker of aspheric lenses and mirrors in the world (now part of Coherent laser system). So I learned all kinds of interesting tidbits, at least, casually from him, while he was still alive. They made the correction lenses for the Hubble, along with nearly all the other big space and ground telescope aspherics, whether NASA or Euro based. Their old obsolete aspheric grinding machinery, going back to the 1950's, was consigned to a special workshop space made available to serious amateur astronomers one evening a week, at least prior to the pandemic.
And jargon differs regionally. They referred to edge cement as "sealant". And when I sold machinist supplies earlier, I worked alongside an ex-NASA engineer, who made the optics for the Pioneer satellite program; and he referred to cement as sealant too, unless we were talking about shoe sole glue or Formica glue. After that, we both worked together again in a construction supply firm, where "cement" had a very different meaning. For awhile I wrote feature articles for a glossy architectural magazine oriented to the pro trade, where conflicting regional spellings and pronunciations had to be ironed, or explained in brackets, prior to publication. For example, what we call a "rabbet" window plane in the US is what the Brits call a "rebate" plane. Then another fellow making miniature versions of these for sake of musical instrument makers deliberately took this mixup a step further, and marketed his miniature versions as "bunny planes". It was a lot of fun juggling all this various terminology around.
No issues with my 110xl, although (a) I bought it new - ie it had not been improperly disassembled and (b) it was from a relatively late production run. It came with the ooh-la-la Linhof engraving but I doubt that makes any difference.
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