If you have been even casually following along with LLFNP you know that, as a rule, I don’t comment on lens build quality because I am not qualified. In my opinion, myself and most photographers don’t know enough about lens internals so when they talk about build quality what they really mean is that the lens is heavy for it’s size and the focus ring is smooth. They are, therefore, evaluating lens build quality like a caveman (1).
Therefore, if you ever hear me talking about build quality or other issues regarding the guts of a lens, it is more or less regurgitated from lens technicians whose opinion I trust.
The following discussion regarding the Zeiss Wobble is essentially regurgitated information I learned from communicating with Christopher Andreyo from Skyllaney Opto-Mechanics.
Christopher is an aerospace scientist and mechanical design engineer with a background in designing complex opto-mechanical devices such as IR/ EO airborne sensors, radar equipment, and laser systems used in spectroscopy and LIDAR. As a photographer, he serviced his own lenses and found that rangefinder lens construction is similar to certain opto-mechanical element translation devices he used to design for lasers. 300-500 rangefinder lenses later, he runs Skyllaney Opto-Mechanics. Chris is also something of a Zeiss optics fan so if you think there is a hidden agenda here – think again.
I don’t personally know Chris or the folks at Skyllaney Opto-mechanics but I have been following them long enough to know that they know far more about the guts of lenses than I will ever hope to know. Recently, they dropped a bombshell regarding Zeiss ZM lenses and the pathology known as “The Zeiss Wobble.”
According to Skyllaney, The Zeiss Wobble is a design issue caused by teflon rollers inside the focusing helicoid that wear out over time.
Table of Contents
A primer on rangefinder lens design
On most rangefinder lenses, in order to prevent the optical block from rotating when the lens is focused, mechanical parts are often used to aid in the stabilization of the optical axis.
On Soviet made rangefinder lenses (Jupiter series), steel set screws, located in channels, are used to prevent optical block rotation. On Leica and Voigtlander lenses, brass fork sliders or a guide rail system are used. According to Chris, “every rangefinder lens design I have ever seen, that utilizes a nonrotating optical block configuration, has some sort of fork slider/ glide rail/ set screw apparatus inside to prevent optical block rotation. Leica M, Voigtlander VM, Canon LTM, Nippon Kogaku LTM, Minolta M-Rokkor, 7Artisans, and even the Carl Zeiss Jena LTM lenses use one of these anti-rotation systems.”
The Zeiss ZM lenses use what Chriss calls a hybrid helicoid focusing system. Although there are metal parts that have muli-start threads that support the focus movement of the lens and accurate position of the RF cam, there are parts of the helicoid system that are not commonly encountered in other rangefinder lenses. Zeiss ZM lenses (with the possible exceptions of the 35mm and 15mm distagon models) use Teflon rollers to achieve the anti-optical block rotation function rather than fork sliders.
In Chris’ experience, over time, these Teflon roller pins wear and gaps form in the tracks the pins are supposed to travel in. When this happens, the dreaded wobble occurs.
This is, therefore, a wear and tear issue rather than a random or idiosyncratic issue. Stated another way, Zeiss ZM lenses, if given enough time and use, are expected to develop symptoms of wobble.
Nearly all lenses in the ZM line are affected but not all lenses have the same internal design
Teflon roller pins are found throughout the ZM line of lenses which should not be surprising because Skyllaney has seen the Zeiss Wobble in the Zeiss ZM 21mm f/2.8 Biogon, 25mm f/2.8, 28mm f/2.8 Biogon, 35mm f/2.8 Biogon, 35mm f/2 Biogon, 50mm f/1.5 Sonnar, 50mm f/2 Planar, 85mm f/4 Tele Tessar, and the 85mm f/2 Sonnar lenses.
Skyllaney, however, has not encountered The Zeiss Wobble in the 35mm Distagon or 15mm Distagon ZM lenses. As such, Chris cannot comment as to whether or not Teflon rollers are present in those two lenses because Skyllaney has never needed to service either lens for issues.
It is probably interesting to note that not all the Zeiss ZM lenses have the same internal design configuration. There appear to have been “silent revisions” to the mechanics of the lens design over the years. Although the ZM lenses appear externally identical, internally, there are minor differences in later lenses with higher serial numbers. According to Chris, “I have not seen them drop the Teflon roller pin design and implement true multithreaded helicoids with fork sliders yet. But to say the say that the original Teflon roller design that they started with over 10 years ago, is still going unchanged, would not be true either.”
I reached out to Zeiss in March of 2021 for comment through the customer service form on their website but have not heard back yet. This page will be updated if/when Zeiss offers a comment or clarification on the situation.
Does this mean that you shouldn’t buy Zeiss ZM lenses?
In my opinion…It depends.
The first thing to remember is that (barring my nemesis, the Zeiss nubbin) in my experience, the Zeiss ZM lenses are optically excellent lenses and can, oftentimes, be purchased for 1/2 to 1/3 of the cost of comparable quality lenses by other manufacturers.
The second thing to remember is that The Zeiss Wobble can be repaired. The Teflon roller pins can be changed if needed. Skyllaney Opto-Mechanics does the repair for under $200.00
Repair and maintenance of anything is always a headache but, for some focal lengths, even if you bought one new and got it serviced every few years, your wallet would fair better than the wallet of someone who opted for a more expensive lens made by another manufacturer.
The real issue arises for people buying Zeiss ZM lenses on the used market. If you are buying one used, and you down know how many owners the lens passed through and/or you cannot confirm how much use the lens had before you, you need to think long and hard about what kind of “bargain” you might or might not be getting because you never know how close to service those Teflon rollers are inside your lens.
Knowing what I know now, I would still buy Zeiss ZM lenses but I am hesitant moving forward buying used Zeiss ZM lenses without a full understanding of prior ownership and use. I am also encouraged that they (albeit silently) have been updating the internals of the lens.
The bigger picture, Leica in the 70’s, plastic parts, and my beloved Summarits.
There is a theme that keeps popping up when I talk with lens technicians. Plastic inside lenses is suboptimal if your goal is to keep a lens forever and create an heirloom for your kids. This issue came up in the 90mm focal range where I was advised against lenses from the Leica lean years of the late 1970’s and 80’s. During that time, Leica went lean on quality control and plastic was used in some of their lenses. These lenses can no longer be serviced.
If, however, you are like me and don’t feel that lenses are investments and you are looking for something you can beat up and take pictures with in the real world, you might be grappling with the question of what kind of expectations you should have for your camera lenses. Should you spend more now and expect lenses to work forever so you can hand them down to our offspring for the next 250 years OR, conversely, is it better for manufacturers to make lenses that they can sell at a more reasonable price with an expected, limited lifespan and/or require maintenance from time to time.
I am writing this post from the confines of a van in the middle of nowhere next to a slot canyon. A few hours prior, I was in the slot canyon with a 28mm f/2.8 Zeiss ZM Biogon dangling from my neck scraping the front of the lens on the side of the canyon. Luckily, I had a UV filter on the front so no damage was done to the actual lens, but that could have caused a permanent issue (2). Maybe I am unlucky but these situations seem to happen to me far too often to believe that lenses are investments and/or I should spend an unreasonable amount of money now to prevent problems a decade from now. If I were a betting man, I would say I have a 50:50 track record of causing more problems for my lenses than plastic parts.
If you are anything like me, I think that there is an argument to be made that owning less expensive lenses and having them serviced or replaced from time to time is a reasonable approach. You already know that I never seem to bring my Summicron 35mm ASPH anywhere because it is too expensive and I am afraid I will ruin it. I have also been known to sing the praises of the Leica Summarit line knowing full well that, somewhere inside, Leica may have taken some sort of half measure to bring the price down to a reasonable level. Time will tell. I just wish manufacturers would disclose what they are doing so we could make informed purchases and know exactly what we are getting ourselves into. Buyer beware.
If your lens currently suffers from Zeiss Wobble it must be addressed because it will, eventually, cause focusing issues. The wobble will eventually cause the optical block to become uncentered on the optical axis.
Disclosures: I have no business relationship with Skyllaney Opto-Mechanics. This is not a paid advertisement. You are, however, encouraged to contact them and follow them on the socials. If you have an even passing interest in lens history or expert technicians doing crazy things with lenses, they are going to blow your mind. Skyllaney Instagram
- The next time you hear a photographer talk about lens build quality, please remember that on the forums, in the YouTube videos, and pretty much everywhere on the interwebs, the Zeiss ZM lenses have always been hailed for their build quality. They are heavy for their weight even with their Teflon rollers. Please listen to the experts and don’t evaluate lens build quality like a caveman.
- I dont have a lens hood for my Zeiss 28mm Biogon lens. I was going to get one but never got around to it. I hate when lenses are sold without hoods. I got lucky this time but, as a rule, I keep a lens hood and UV filter on my lens at all times.