Zeiss ZM Lenses
|Coding for Digital Use|
The Features, as Described by Zeiss...
Excellent Image Quality
The Carl Zeiss range of T* ZM-mount lenses offers the highest possible standards in terms of performance, reliability and, of course, image quality. Quite simply, they are superior in every way. You can count on highly advanced flare control for crisp and brilliant images, for example. And virtually zero geometric distortion, ensuring precise accuracy when reproducing shapes – especially useful when photographing products and architecture.Minimized Focus Shift
Carl Zeiss T* ZM-mount lenses are specifically designed to minimize focus shift with aperture changes – an important innovation with big benefits for rangefinder photography. As a result, you can expect improved accuracy of the rangefinder-defined focus. While the precise 10-blade aperture with 1/3 stop interval click stops ensures exact exposure.Ideal Aperture Properties
Photographers want to guide the observer through the image. Minimal depth of focus is often used as a design element. This keeps the background intentionally blurred to keep the attention of the observer on the main subject. The ZM lenses feature ten aperture blades. The almost circular aperture helps to create a particularly harmonious effect in the out-of-focus areas of the picture (bokeh).Smooth, Precise Focusing
Manually focusing a lens means controlling the image result from your fingertips. A good ergonomic design makes all the difference. The user-friendly focusing ring on ZEISS lenses with an ergonomic finger rest is perfect for fast, precise focusing. Changes are immediately visible in the viewfinder. The high-quality focusing mechanism moves smoothly without play, thus also supporting the intuitive interaction with the focal plane.Robust Design
The mount and control elements of all ZM lenses are made of metal and are designed for decades of intensive use. The high-quality craftsmanship of the all-metal mounts, the easy-to-grip metal focus and aperture ring and the robust front bayonet and filter threads ensure an amazing photographic experience.
A general look at and review of the Zeiss ZM lenses, covering all things they have in common as far as build quality, optical performance, accessories, look and feel, coding for digital use and known issues.
ZM lenses, while designed by Carl Zeiss and which are based on their traditional optical formulas - are manufactured and assembled by Cosina/Voigtländer in Japan - save for two. The two lenses that are the exception are the Distagon T* 2,8/15 and Sonnar T* 2/85 ZMs, which are assembled in Germany. The latter has actually been discontinued as of April 2011, leaving just the former. These are highly specialized lenses due to their focal length and speed, and are in a bit of a niche. As such, they're also very expensive.
There's an old saying in the IT industry that says, "nobody ever got fired for buying IBM." The same axiom could apply to the ZM lenses. There really isn't a bad one in the bunch.
In this review, we'll cover the basics that apply to all of the ZM lenses. From here, it is suggested that you read the individual lens reviews (which are linked to below) to see how each lens handles and performs.
The ZM line of lenses represent a well thought-out system. They benefit from being released in a short span of time, as all share a common design as far as external look and feel, image qualities, accessories (e.g. hoods and caps), etc. Unlike Leica and Voigtländer, both of which have longer histories - all ZM lenses are ergonomically and visually very similar. This makes switching lenses a thought-free process and ensures consistency among your images as far as color response, bokeh and other image qualities.
All ZM lenses are made entirely of metal; mostly aluminum and brass. The only plastic you'll find on them are the lens caps! When compared to Leica or Voigtländer lenses, the ZMs feel lighter. They don't have the sheer density that Leica lenses seem to have, which is arguably a good thing because ZM lenses tend to be larger than their Leica equivalents. Mechanically, the controls are all smooth and accurate feeling - not quite up to the level of Leica lenses - but better than Voigtländer. More refined.
Unlike Leica lenses, which are constructed of black-anodized aluminum or chromed brass - there is no difference between the black and silver ZM lenses as far as underlying material. Black ZM lenses have red and white paint filling the engraved markings, whereas the silver lenses have blue and black paint.
The ZM lenses can be generalized as all having excellent sharpness from wide open that improves only slightly stopping down - and mostly into the corners and edges of the frame. While there's typically some vignetting in the early part of the range, it is modest and clears up quickly. Distortion is another metric by which lenses are judged, and perhaps no surprise here - all ZMs offer very low, almost non-existent distortion. They are very well corrected in this regard. Using a camera like the Leica M8 or M9, which lack anti-aliasing filters in front of the sensor really let these lenses shine. The M8 in particular makes for astounding images due to the crop sensor effectively trimming any vignetting or softness from the periphery of the frames. No matter the medium - be it film or digital - the ZM lenses really deliver and do so across the board.
Another aspect that they all share is a matter of contrast. That is to say, they all have a fairly high, or "modern" contrast. This is somewhat surprising as this look is often associated with Leica "ASPH" (aspherical) lens designs - yet not a single ZM utilizes aspherical elements (partly why they tend to be larger). This is because of their design heritage, utilizing designs that have been proven (and perfected) over a long period of time. In their infancy, a lot of attention was paid to minimizing flare and reflections because of the limits of technology. Surface to air interfaces (which induce reflections) were minimized as much as possible, for example. With the advent of the Zeiss T* coatings, improved anti-reflective baffling and painting of the interior surfaces and computer-aided design - the ZM lenses could indeed serve as a benchmark for anti-flare performance. Most are highly resistant to flare and reflections, even without the use of a lens hood and with the sun directly in the frame!
Because of their excellent performance as far as flare and reflections go as well as the high level of contrast, colors are deep and saturated. This is especially evident in blues but also greens and reds - though any color juxtaposed against another really pops.
The "bokeh" or out-of-focus rendering of details is also rather similar across the range. Details are gently blurred, so you have an idea of what's there, while remaining very pleasing visually and soft. Of course, part of this is because none of the ZM lenses are particularly fast - f/2 to f/2.8 is about the norm, with the C Sonnar T* 1,5/50 ZM being the single exception - which has a character uniquely its own. If there's one lens that stands out in this regard, it's this one and that's because of its classic Sonnar formula (and thus the "C" designation, which also means "compact"). Another aspect affecting bokeh is the fact that all ZM lenses have ten aperture blades. This serves to create a very round aperture - imparting rounded, rather than geometric out of focus highlights as is common with fewer blades.
Some describe Zeiss images as having a sort of "3D look" to them. While many lenses and not just Zeiss are capable of producing this effect, Zeiss lenses do seem to have a certain knack for it if the conditions are right. The ZM line is no exception. Between the outstanding sharpness of the focal plane, the pop of colors, the transition of in- to out-of-focus areas and even the alignment of the planets in some cases - can lead to an interesting, almost "3D look" to the images. Many have tried to explain the cause(s) of the phenomenon, none have succeeded - but everyone knows it when they see it.
Not so much accessories, but since the lens hoods are a separate item to purchase (they're not included) and the fact that they're almost unncessary with the great flare handling - we're going to call them that. Each ZM lens has a hood available for it; sometimes the hood can be used with multiple lenses (even if it's not so marked). Like the lenses, they're made entirely of metal and painted with a semi-gloss black on the outside and a flat-black on the inside, serving to further reduce reflections. In most cases they are "vented" or have slots cut out to improve the view through the finder. They all have a bayonet fitting on them, which makes mounting and unmounting them quick and easy. While the flare handling of the ZM lenses is extraordinarily good, we still recommend getting a matching hood for the lens. It makes them just that much better as far as stray light - but also offers mechanical protection for the front element.
As mentioned, the lens caps are the only plastic you'll find on ZM lenses. Unfortunately, while the idea behind them - so-called "pinch caps" - was a great decision... The execution, across the board - falls flat. They're very light, bordering on flimsy. But the real shame is that the grooves/knurling on the pinch tabs runs perpendicular to how they should. This means that in practice, they tend to be somewhat fidgety, slippery affairs. Though this is mostly the case when using a lens hood where placement is more critical as is the need to verify that they're truly secure. Most folks don't particularly care for the lens caps - and justifiably so.
See the paragraph above regarding the lens caps. Long and short of it, they work - but stink.
Unfortunately, as perfect (or darn close to it) as ZM lenses are optically - they can fall a bit short mechanically. There's no particular pattern to these issues, so it's mostly a matter of "luck" in experiencing either of these two... While relatively rare, these issues have happened to enough people that they're worth mentioning. Therefore it is probably most wise to purchase your ZM lens(es) from a reputable dealer new - which nets you the standard three-year warranty. In either case, out-of-warranty repair can be fairly expensive all things considered and involve a stretch of downtime. You can expect a 270€ bill for such repairs! On the bright side, these issues do not appear to be indicative of a design failure on Zeiss' part but rather the assembly and quality control thereof by Cosina/Voigtländer.
The first issue is generally known as "the Zeiss wobble." What happens is that a lens group or retaining ring loosens up. As a result, there is a detectable wobble of the front half of the lens when rocked side-to-side as compared to the back half. While we've never heard of a single lens falling apart or failing to perform optically due to such a condition - the fact remains that this shouldn't happen on a lens of such caliber. It does detract from the experience but is mostly harmless. On some lenses, the retaining ring in question is easily accessible from the back of the lens and can be tightened up by yourself (with all due caution exercised).
The second issue is a bit more insidious and stems from either improper or insufficient lubrication. The grease on the focusing helicoid displaces and/or is of the wrong type - and causes rough/slipping focusing action and even squeaking in some instances. If you're lucky, cycling the lens between hot and cold and exercising the focus ring from lock-to-lock will somewhat correct this - or at least buy you time - before service is necessary. And it will be necessary sooner or later as this doesn't go away on its own.
While somewhat aggravating, neither of these issues are showstoppers, and as mentioned earlier - can happen randomly. You can experience one or the other or even both - but no particular lens is more prone to them than another. We will reiterate that it's probably a good idea to buy your ZM lenses new and from a reputable source, where you have three years from the date of purchase to have these issues addressed under warranty.
It is unfortunate that Zeiss chooses to make customers pay a rather steep price for service on such-affected lenses out of warranty. While it's obviously an assembly and quality control issue, Zeiss' name are on them and are supposedly "subject to stricter quality control" which is up to Zeiss standards... It is our opinion that they should do the right thing and offer customers experiencing these particular issues a discounted or even free service.
Another minor issue that tends to happen is an inconsistency in focus damping "feel." Even on the same model of lens, one might be relatively loose and easy to turn while another is somewhat tighter, with more resistance. The more ZM lenses you have, the more noticeable this will likely be.
Finally, something to keep an eye out for (mostly on older ZM lenses) are the framelines that the lens brings up. They're designed for use on the Ikon before anything else, and what's good for the Ikon might not necessarily be what's best for Leica M bodies - especially digital ones such as the M8/M9 where framelines are one important half of the equation to coding them (the bit pattern on the mount being the other half). This can force you to code a lens sub-optimally. While under warranty, Zeiss will swap the mount if requested. This further underscores the importance of buying new from a reputable dealer.
Coding for Digital Use
"Coding" of lenses for use with digital Leica bodies - the M8 and M9 (and all variants) - is accomplished by the machining of pits into the mount flange, which are then filled with either black or white paint and represent a "code" (bit pattern). In most cases, only the black mark is really needed as the silver of the mounting flange acts as a white bit. These bits are read by an optical sensor located on the mounting flange of the camera. Unfortunately, no one other than Leica offers this on their lenses and is often required for the best (or even usable) results with third-party lenses. While Leica will (for a fee) perform this service on non-coded lenses, they will only do so on Leica lenses.
You are left with three options. The first is to find a service person that will machine these pits for you, which you can then fill in to code as you like. The second option is to replace the mounting flange with a custom-made mount, fabricated of brass by John Milich (the so-called "Milich adapters") of Brooklyn, NY. These custom flanges are of excellent quality and get the job done; but are relatively expensive. Especially if you have several lenses to do. It also involves some careful removal of the screws requiring acetone to break the thread lock compound applied at the factory. Some have taken to using a Dremel tool and making their own pits. This is rarely pretty, can affect resale value and the possibility of incorrect positioning of the pits or metal shavings entering the lens are high.
The third option is to "hand code" your lenses, which unfortunately - is a bit of a temporary fix. This is accomplished by using a template (such as the Match Technical D-Coder ring) that is fitted over the flange and the pits marked with a black Sharpie (or other permanent, deep black) marker. The problem is that on flat mounting flanges and the tight tolerances found in the M system - through normal use by mounting and unmounting of lenses, the marks will rub off eventually. This depends entirely on how often you change lenses, of course. Thankfully, as opposed to earlier versions - Zeiss has switched over to a slightly modified flange in later versions, where a very slight groove is machined in - which will hold the coding marks much, much longer.
One further issue to complicate things is the fact that on some earlier lens versions, there can be a screw located precisely where one needs to place the coding marks. In most cases, while not pretty - either doesn't matter since there need not be a black pit in that location - or can be filled in enough to trigger the proper code. Zeiss started to address this in later versions by moving the screw in this area.
One thing to keep in mind when coding the ZM lenses for digital use is that you're using profiles created for Leica lenses. While the corrections come very close, they won't necessarily be exact. That is why, in practice - one usually selects the closest equivalent lens. Though in testing other lens profiles, sometimes it is preferred to use another. Usually what is listed in the Leica Lens Codes list or mentioned in the "Coding for Digital Ms" sections of our reviews - will be your best option. Properly coded, the lenses will work just fine - any small differences really are just that, and not an issue.
When using lenses with the M9, more so on the wider side - it's highly recommended to update your body to at least version 1.162 of the firmware. This version was released mainly to address the "red edge" issue (where one or more edges take on a red tint). The corrections in this firmware go a long way over the previous and in most cases eliminate the issue. In any event, you can always use CornerFix to correct images as well.
The Zeiss ZM line of lenses, optically - are essentially as good as it gets. Combined with a cost far less than their Leica equivalents makes them very attractive. Some just prefer "the Zeiss look" and these lenses don't disappoint by any measure. Mechanically, or perhaps more accurately - manufacturing-wise, there is room for improvement between "the wobble" and lubrication issues. Though slight, the chance does exist that you could be afflicted. While it would also be nice to have a better coding solution, it's worth noting that Voigtländer and other third-party lenses all have the same limitation and shouldn't reflect negatively on Zeiss. Just that if you're looking for a truly "plug and play" solution, you're going to have to suck it up and buy Leica.
In any event, any or all of the ZM lenses will reward you with stunning optical performance at a moderate price point. They really do fit well in between Voigtländer (where they're better optically) and Leica (where they're lesser mechanically). They fill a particular niche in the market and reward the Zeiss Faithful as expected. You shouldn't hesitate to consider any or all of them.
We've published several in-depth reviews of individual ZM lenses in our Reviews section. Check back occasionally as more reviews will be forthcoming as well as the enhancement of existing reviews with additional content and testing. At this point, the following ZM lenses have been reviewed:
- Zeiss Biogon T* 2,8/25 ZM
- Zeiss Biogon T* 2/35 ZM
- Zeiss C Sonnar T* 1,5/50 ZM
- Zeiss Planar T* 2/50 ZM
Zeiss has been releasing articles in their "Camera Lens News" newsletters about the naming of and providing more information on their lens designs:
- CLN39 (03/2011) - Tessar
- CLN40 (07/2011) - Planar
- CLN41 (12/2011) - Distagon, Biogon and Hologon
- How T*-coating made glass invisible
They've also posted a two-part article on how to read MTF charts:
- How to Read MTF Curves, Part I
- How to Read MTF Curves, Part II
- How to Read MTF Curves, Part II - Sample images
For reference, we're archiving the PDF copies of these articles for your reading pleasure.