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Plastic "King of Bokeh"


Gus Lazzari

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<p>My problem with the whole thing is not so much what the thing is made of, but that they now want to sell us pot metal, plastic and cardboard, etc., at the price of machined steel or brass.</p>

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<p>I was astonished to learn that the back door of my wife's Leica Titanium M6 was made out of pot metal. Some fellow here, not long ago, was posting how he went about repairing a broken hinge on his Leica M6 pot metal back door.</p>

<p>Again, I wonder what the back door of a Leica MP is made of? Hopefully, it's brass or steel.</p>

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<p>Gus is much more knowledgeable about the composition and maintenance of Leica lenses than I ever will be, but I believe that the presence of a polymeric material (polycarbonate) is hardly a design fault. Modern use of materials, from the last half of the 20th century, has shown that the best designs often comprise a multitude of basic materials, which act in concert to provide an overall optimum result from the point of view of weight, performance, stability, and so on. Metals, ceramics, cermets, polymers, glass, glass-ceramic composites, and combinations of these, go into functional components of planes, cars and many other critical aplications, so why not cameras as well?</p>

<p>Perhaps Gus can inform us of the difference between the German made chrome version of my 50mm Elmar-M lens and its black version, but the difference in weight is great. I prefer the much lighter black version and couldn't care much about whether Leica has "sneaked" some plastic into the interior lens mount. Give me adequate longevity of the lighter weight and equal optical performance, anytime. Whatever its composition, I made a great mistake by selling my Midland Summicron version 4 lens, which it's current price has now put it out of reach (I can justify more the ASPH version, even pricier, for its significantly better overall performance, though less smooth Bokeh).</p>

<p>The M4-2, that saved the M series from extinction, made a few materials concessions to the former M4 in not very critical areas (stamped metal exposure counter rather than an engraved dial), but also improved the metal of the winding mechanism gears (case-hardened or a similar hardening process) which had previously been of less strong metal. While improved from one materials specification viewpoint, this apparently required more frequent servicing after heavy use.</p>

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<p>Arthur,</p>

<p>According to Sherry Krauter, the glass elements of my Elmarit-M 1:2.8/21mm are held in place with glue rather than retaining rings. She wouldn't even risk performing a CLA on the lens because you need to use a heat gun to release the glue. The cheap gluing technique is in addition to the lens having several plastic components. Those visible on the outside including the aperture and focus rings. Absolutely unacceptable, in my opinion. This was not in an effort to save weight, but rather save Leica production costs, unfortunately, at the price of their formally impeccable legacy of uncompromising build quality.</p>

<p>I wonder if Holga uses the same high-tech polymers and glue? Or maybe even my vacuum cleaner? I sure want that to be light-weight.</p>

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<p>Robert,</p>

<p>Is the glue between some of the elements (as convex to concave), which if I'm not mistaken is quite normal (in fact Leica Canada had access to a type of balsam glue that Wetzlar did not and which conferred certain advantages over previous glues), or is it, as you seem to say, to physically hold them in place in a lens mount assembly? That may make a lot of difference and differentiate your Holga example from a Leica lens. Carbon fibre, like polycarbonate plastic, is an organic material, not metal. But I think nobody has put down carbon fibre as inferior, although few understand the difference between engineered plastics and cheap plastic wrapping or plastic toys.</p>

<p>Metals and alloys themselves vary widely in mechanical properties. There are many that shouldn't be used in lens mounts (question of differential thermal expansioin, hardness, strength, etc.). However, I hear few who distinguish betwen metal quality, only a continual tirade against organic materials. What we need in this continuing discussion is the opinion of someone involved in designing high quality lenses and widely knowledgeable about the nature of and the difference in materials, not only popular opinions. It might otherwise require readers to take a course in materials, to describe or appreciate the differences and applicabilities.</p>

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<p>Arthur, I don't think Canada Balsam is used any more for making cemented doublets. I believe it doesn't endure as well as more modern adhesives. I think the problem may be that it is too susceptible to fungus formation, or separation.</p>

<p>The idea of gluing elements into premium lenses is upsetting to me. Surely they cannot be adjusted and fine-tuned with the precision of threaded parts. They are certainly not meant to be worked on. what are we supposed to do when they are ready for a CLA? Throw them out, like last year's cell phone? I hope my 21 and 24mm ASPH lenses were not made in this way! Or my 35mm ASPH Summilux, for that matter.</p>

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<p>Rob, presumably the normal CLA does not need to separate, clean and re-cement lens doublets (Unless I possessed optical laboratotry equipment, I would hesitate such fine re-building). Have you heard of any real cases where the film between the doublets has changed its optical qualities to need replacement? Almost any device will be attacked, of course, if put into extreme conditions of humidity, heat or cold, and I expect that when problems occur it is often because of maltreatment of sensitive equipment. I wouldn't worry about your fine lenses. My 21mm ASPH has been in continuous use for about ten years now and it appears as new as when purchased (no glass surface hazing, and the helicoids are as smooth and play-free as when purchased). This is also true for the 35mm ASPH. I don't lose any sleep worrying about their possible quality issues.</p>
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<p>Arthur,</p>

<p>You misunderstand.</p>

<p>I am not talking about the cement between glass elements but rather the fact that it is glue that holds the individual glass elements in position within the lens tube, rather than screw-in retaining rings.</p>

<p>The glass elements are held in position within the lens barrel by glue alone! As Gus said:</p>

 

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<p>Adhesive is required to seize up the group into it's alignment.</p>

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<p>Robert,</p>

<p>Thanks for your comment. I understood the two possibilities, of course, and was just looking for a clarification as to which. I have not heard of Leitz or Leica lenses with elements held in place SOLELY by glue. I can see glue being inserted into a mechanical slot, but not without the latter (mechanical slot) to hold the lens elements in proper alignment.</p>

<p>However, the bottom line, as Ray suggests, is in the use. When we see are able to see degraded results in images made with Leica lenses, owing to their particular materials of construction, we can start to be concerned. My experience of practical use, excepting one 50mm lens which demonstrated a bit of wobble in the helicoidal focus mount (brass on aluminium alloy) after 20 years, has been quite positive. I also respect the fact that Leica lenses normally arrive with perfect alignment of elements (centering) whereas my Voigtlander lenses have been known to have occasional decentering upon manufacture (the cost/care of assembly is of course more restricted in the case of the much cheaper Cosina lenses).</p>

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<p>Arthur Hooper's clarification applies to my post as well. I was referring to gluing the lens groups into the cell, and not to cementing together the elements that comprise a cemented doublet, which is of course an accepted and time-honored technique. Obviously glueing together an assembly can't be done with the precision of adjustable threaded parts. And of course, no one expects the separate elements of a cemented doublet to be separated during a routine CLA. It seems to me that a lens assembled in such a way can't be dismantled for cleaning, at least by ordinary means, as Sherry has evidently said.</p>
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<p>Quite apart from the technically related discussions (or lack thereof) of engineering plastics versus metal, the historical stygma of cheap plastic toys and so on, what bugs me most is the continued underlying theme in many past OP's in this forum which imply "if it isn't made of metal or isn't (or wasn't) made in Germany, it must be junk" mentality of some elitists. The Ontario plant was a major innovative player at a critical time in the progress of Leica, the source of many great Leica lens designs, the saviour of the M system after the commercially disastrous German M5, and a turning of the corner when Leitz needed to improve the economics of its cameras and lenses to survive. When it became more sustainable and when the conditions in Germany werre improved the new company decided to move the facilities back to Germany (except the exacting military applications/facilities which were sold to a US company). Despite this, the words "made in Canada" seem to have that magical quality of some Neanderthal activity in the northern boondogs, for many who have little knowledge of the Midland plant and the manufacturing environment in which it was located.</p>

<p>Many practicing photographers I believe are little interested in such snobbery.</p>

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<p>Arthur, Francisco and John G: The key here is that these lenses are in a failure stage of their life cycle. This can only be attributed to Leica's bad choice of materials in certain <strong>critical</strong> areas of this crop of lenses.</p>

<p>I'm with John Shriver on this one.<br>

Time has borne this out; their use of <strong>"plastic"</strong> is exclusive and contributed to the direct cause of those failures. </p>

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<p>Gus, maybe there are other factors not made in the plant. I know of some who have lenses of all metal components (other than the glass elements) and which would have led a long life if their owner hadn't insisted on photographing frequently and without care in wind blown fine sand beachside conditions. The lenses eventually quit focussing and I can only imagine the state of the metal helicoidals and other interior parts of these badly cared for lenses (On the Moh's scale of hardness I believe quartz sand is as high as 9, while diamonds are 10 and many metals somewhere near the middle of the scale, much softer). One also hears horror stories of lenses and cameras being submitted to moist and hot conditions, being left for lengthy periods in the overheated glove boxes of cars, and so on.</p>

<p>So how do you relate the observed terminal condition of the lens to both the plant where it was made and its subsequent history of use? Do you also see terminal conditions with mainly metal lenses? </p>

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<p>Origin of manufacture isn't really an issue here, but this common condition of outright thread failure is.</p>

<p>Metal helical tubes may have been damaged by debris such as sand, but you can always rehabilitate the metal with courses of a "lapping" compound treatment. (This re-polishes the threads) With ultra cleaning and then a reapplication of the correct grease, it feels close to original.</p>

<p>But metal is ruined by catastrophic impact related damage. Out of shape aluminum is nearly impossible to message back to a perfect circle. Plastic can sometimes "snap" back.</p>

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<p>Thanks, Gus, for bringing these issues to the light. In spite of my questions, it has changed my own perception of the company. It would be even more useful if Leica read this OP. Many of the new Leica lenses are priced outside the range that many of us can afford (and that of the competition), so we should at least expect uncompromising quality. I would hope that Leica at least has the good sense to touch base occasionally with principal independent repair persons such as yourself and others mentioned in this thread, in order to obtain additional professional feedback on the durability of their products. </p>
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<p>This long thread was kind of hard on me, I admit. Lots of misunderstandings due to overly fast reading/writing, lots of generalizations worth nothing at all, well-well. What this thread has given me, though, (apart from Gus' hard facts) are interesting questions:</p>

<p>1) May glueing-in lenses be even more precise than holding them in place by retaining rings?<br>

(I imagine this to be probable – depending on the place of the lens within the design.)<br>

2) Does any of the oft-mentionned repair-gods have some half-way serious statistic up his/her sleves on how many of those Candian pre-asph 35-summis have become useless because of *literally* broken plastic parts? Does Leica? (Hair fissures don't count as they do not inflict dysfunctionality (yet))<br>

3) I definately do not fear getting bashed/laughed at by plastic-lens-totin' Canonians/Nikonians/Sonyists. Am I part of a minority amongst Leica users?<br>

4) As far as I understand the matters, glued-in-place lens sets (as in the 21mm) should be totally immune to dust/moisture/mould entering as well as to vibrations causing element to go out of alignment. Consequently, I would *love* to see this attribute in all of my lenses. Again, am I alone there?<br>

5) Why not applaud Leica for potentially 'sturdier' construction and for keeping indie-repairers without collimators from disassembling lenses and returning them with possibly lower perfomance specs?<br>

6) Has anyone asked Leica about their ability to replace the old plastic parts with new/metal ones yet?</p>

<p>I always believed that good questions help a discussion more than simplistic answers.</p>

<p>Cheers, Pete</p>

 

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<p>The last responder has at least a few facts or questions right, but has clearly missed a few others.</p>

<p>1) Gus' hard facts apparently come from the one lens he has depicted, and perhaps a few others of the ilk.</p>

<p>2) Nobody has mentioned how many post 1980 lenses have been constructed using so-called "inferior" plastic parts and glued assemblies. The all too brief mention of the glued in lens elements of the 21mm lens needs to be substantiated (which one? the f3.4, the older f2.8s or the current ASPH f2.8?) rather than just freely tossed out.</p>

<p>3) How can it be assumed so easily that simply because the elements are glued in that they make the assembly free of dust, moisture, whatever? What about the appearance of a discontinuity in the glued section or its disattachment?</p>

<p>What we need, other than speculation and a few hard examples of poor condition, is a discussion of Leica and Leitz manufacturing practice, and how that has varied (a) over time and (b) from one lens to another. Also © why such variation and design principles were chosen by the company.</p>

<p>There may be other persons of first hand knowledge, but the only one I know of who might have a handle on that is Erwin Puts. Whether or not he reads this forum I know not, but it would be interesting to have someone who has been involved with the manufacturing to discuss the issues raised.</p>

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<p>First of all, I've never encountered a lens intentionally glued into it's seat. (Too messy & unnecessary) It's typically a "Locktite" applied to the <strong>retainer ring</strong> threads. Aged lenses may seem to be glued in, but it's instead the tight tolerances being taken up by moisture/fungus corrosion, or migrated thread Locktite, or flare paint and/or plastic that has changed it's original composition and expanded chemically.</p>

<p>Now some companies (<strong>Not</strong> Leica M or R lenses) to avoid the costly metal threading & retainer design; melt & bevel the lens elements into their seats and are therefore rendered un-serviceable. (Not dust or humidity proof)</p>

<p>I've stated this before: The seats are permanent & completely reliant on the quality of the original manufacturing.<br>

In production lenses; centering, axis, flatness etc. <strong>aren't</strong> service variables to adjust. Absent heavy shock or impact, <strong>quality</strong> lenses & their lens elements / groups, can be carefully re-secured tightly after a disassembly without <strong>any</strong> change in performance. (Infinity focus adjustment / collimation is the only service variable)</p>

<p>In addition, plastic lens holder units have issues with <strong>aging</strong> & the chemical changes that follow; causing:</p>

<ol>

<li>Tight tolerances to expand which causes binding. (Can make element/group extraction, very hazardous)</li>

<li>Retainers to "bite" causing a problem with "feel" as it relates to element torquing pressure. (Also, very easy to cross-thread a retainer)</li>

<li>Hardness loss so threads fail upon torquing. (TDC index mark misalignment)</li>

<li>Solvents normally considered safe when the plastic was new, now can't be used.</li>

<li>Debris like sand etc. which can easily & permanently gouge the smooth helical tracks or threads.</li>

<li>Plastic zoom helical, roller guide metal screws, <strong>strip out</strong> with <strong>minor</strong> shock or impact.</li>

</ol>

<p>Precision metal construction rarely has any of these issues.</p>

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<p>Thanks, Mr. Lazzari. I for one find your knowledge most helpful. For those interested, it would be nice to know how Leica lenses have evolved over time, from the manufacturing concession (if any) point of view; we are aware I think that considerable progress has been made in lens performance over the years.</p>
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