Voigtlander Nokton 50mm 1.5 II VM and Zeiss C Sonnar T* 50mm 1.5 ZM: a comparison
I have had an eye on the Zeiss C Sonnar T* 50mm 1.5 ZM since I purchased my first Leica M camera, the M typ 240. I see the world in 50mm, and I could happily use just that focal length for the rest of my life for everything if I had to. The different 50mm options for me were few: the Leica ones were too expensive, so I didn’t even consider them at the time. I wanted the fastest thing I could get, so I bought the Voigtlander Nokton 50mm 1.1 VM. I had the bokeh bug at the time. I soon realised how big and cumbersome that lens was on a Leica M and started looking around for a smaller but still fast option. The options were just three: The Sonnar, the Voigtlander Nokton 50mm 1.5 Aspherical VM (review here), the Zeiss Planar T* 50mm F2 ZM. Thread mount lenses were not what I wanted. Of these options, the Planar and Nokton were modern designs with few known flaws, the Sonnar was renown for a bit less sharpness but especially severe focus shift.
But the Sonnar was so tempting: so small, handling was light-years better than the Nokton, it was the speed I wanted…but that focus shift kept me away.
Fast forward to end of 2020 and many, many lenses later: I have bought and sold many, tried several samples of some, I have been restless in my search for my ideal lens. Ergonomics are almost as important as the optical performance for me: if I don’t enjoy using it or worse, I have to fumble/fight it, I just don’t like it. That’s why I had 6 (yes, six!) copies of the Nokton and could never bond with it. You can read about why in the Nokton review here. In October 2020, when at last I had settled on the Planar, a really great lens and for a great price, Cosina decided to throw a wrench in the works: they announced the Voigtlander Nokton 50mm 1.5 II VM (review here).
I had said to a friend just a couple of months earlier how I dreamed of a lens with the optical quality of the Nokton in the body of the Sonnar. That would be my desert island lens. Those were my words. So what happened? Cosina announced exactly that! I couldn’t believe it. The optical design was new but I trusted Cosina: the latest releases have been nothing short of spectacular. I bought it as soon as it was released and have been using it ever since.
Why do I have the Sonnar in my hands then? Well, I still have it because I bought it for my 50mm Leica M lenses comparison and I wanted to review it individually and then compare it to the Nokton II. Was I right in holding off and not buying it? Read the review to find out!
So, what are the differences between these two incredibly similar lenses?
Handling
The size of the Sonnar and the Nokton II is just perfect.
Both lenses are really small for their specification. In my opinion they are the embodiment of what a Leica M should be in size, even at this speed. The Leitz Summilux 50mm 1.4 E43, or Version II, reviewed here, was of a similar size, just a little longer. In my opinion it’s the best sized Summilux 50mm.
Let’s start with the physical measurements: the Zeiss is 38.2mm long, the Voigtlander slightly shorter at 36.9mm. The diameter of the barrel is 55.5mm for the Sonnar, 52.3mm for the Nokton. The maximum diameter at the focus bump/aperture tabs respectively is barely 3mm more for both lenses. These measurements make these fast prime lenses diminutive, especially given their speed. Neither is better in size, they are barely distinguishable in use.
The weight is a bit different: the Zeiss weighs 250g, the Voigtlander 198g. If 52g seem insignificant on paper, in use I can really feel the difference. You feel the additional weight of the Sonnar. There is a nickel brass version of the Nokton that weighs 255g. I haven’t handled it, but when I bought my copy I intentionally went for the lighter version: I wanted to take full advantage of the smallest size and weight.
Is that diminutive size a problem? Not at all. Both lenses handle beautifully. No problems distinguishing between focus and aperture rings, there is a good knurled grip around the base to easily mount/unmount the lens, and the knurled focus rings work perfectly, there is no need to use a tab for lack of space.
Both lenses feel solid and well built. The Zeiss feels slightly more dense, but that’s just the extra 25% in weight. I see no difference in the build quality. After all, they are both built by Cosina in Japan. Cosina owns the Voigtlander brand and manufactures most Zeiss ZM lenses. In fact, the two lenses share the same mount flange, the same bayonet hood system (just a different size) with the controversial chromed brass front ring. The Nokton has a 43mm filter size, the Sonnar 46mm. Both come without a lens hood, which is optional. In both cases it is a bayonet mounted vented circular metal hood which works beautifully.
Let’s talk about the ergonomics:
The Voigtlander Nokton 50mm 1.5 II VM has a focus ring with a double knurled profile reminiscent (intentionally) of an old Topcor lens. It has a fairly dampened action but it feels buttery smooth and makes it very, very easy to focus precisely. The aperture ring is tabbed and the tabs are placed asymmetrically around the circumference to be closer to the top of the lens. This design might be historically true to the Topcor but it just makes the lens less good ergonomically: it’s not easy at times to change aperture on the fly because you can’t find the tabs immediately. Fumbling is bad, and it could have been avoided with a design like the Sonnar’s. On a positive side, the detents are firm enough to stay put but easy to move when needed. Perfect.
The Zeiss C Sonnar T* 50mm 1.5 ZM is even better than the Nokton: nice knurled focus ring with medium-light dampening that can be moved with a single finger tip thanks to the focusing nub under it, which is found on all lenses in the Zeiss ZM line and offers the best of both worlds in my opinion. You prefer tabbed lenses? The nub works perfectly well in the same way. You prefer a focus ring like me? The nub disappears in use and you’ll never notice it. Great. The aperture ring is a proper one, knurled around roughly 110 degrees. The aperture values are engraved on the smooth arc of its circumference on the upper side of the lens. The aperture moves in thirds of a stop and the detents are nice and firm. This lens is a joy to handle.
A minor nitpick that I found to be significant in use: while the Sonnar is simply as it should be, the nitpick is about the Nokton. The mounting alignment mark on the base of the lens barrel is not a raised dot like all Leica, Zeiss ZM and most other Voigtlander lenses. It is a tiny engraved line in the side of the mount flange, barely visible and impossible to locate by feel. Which means that you have to look closely at the lens to find it to mount it and you just go by trial and error in the dark. Dumb. Historical reference: check. Ergonomics: who cares? Dumb.
Lastly, these two fast prime lenses have a fantastic balance on the camera. Actually, the Nokton is so light that the camera points slightly upwards when hanging from the strap!
Talking about the use on camera, both lenses have no viewfinder blockage without the hood, just a hint at MFD, minimum to moderate with the hood mounted and at minimum focusing distance (MFD):
Let’s put the specifications together:
Let’s talk about the performance
The Voigtlander Nokton 50mm 1.5 II VM and the Zeiss C Sonnar T* 50mm 1.5 ZM are very different lenses inside. Or are they? The Nokton is a modified double Gauss design with 8 elements in 7 groups, one double sided aspherical element. Very modern design. The Sonnar is, surprise surprise, a Sonnar design, with 6 elements in 4 groups and all spherical surfaces (the original dates back to 1932!).
We can start with the performance at infinity, then at MFD.
Infinity performance
To better assess the difference between the two lenses we will be looking at an image split in two halves. The Nokton on the left, the Sonnar on the right. This is the full scene:
DISCLAIMER: the crops we will be analysing are 300% crops. Why 300%? Because it’s nice to see the castle filling the crop. This is pixel-peeping to the extreme. Take it for what it is, in real photography you will hardly see the minute nitpicks we will be talking about here!
Let’s roll. Centre crops:
Wide open I don’t see that much difference in the centre. They really look the same. A little spherical aberration is masking the finest details but they are both impressive. At F2 shows a bit more detail and both lenses show more contrast. At F2.8 they just go their own separate ways: the Nokton keeps on improving the detail rendering and eliminates the spherical aberration. The Sonnar worsens dramatically: the change is stark, it just goes soft. And it stays soft until it starts recovering at F5.6, returning to F2 levels at F8. Wow, that is some focus shift! The Nokton simply excels, peaking at F5.6.
Mid-frame:
There is a clear mid-frame dip in definition caused by the wavy field curvature on the Nokton, but the Sonnar is even worse. Both lenses are not excelling wide open in mid-frame. Both have slightly lower contrast at F2 as well. The Nokton jumps forward in definition at F2.8 and the image becomes of very high quality. It peaks again at F5.6, where it is sharp as tack with a very clean image devoid of aberrations. The Sonnar sees some detail creeping in at F2.8 and the image is getting quite good at F4. At F8 the detail is really good and there is a little more micro-contrast. Still, there is a really clear difference in the quality of the image even at F8: the Nokton is the better lens, no question.
Corner:
Now there is a vast difference between the two optics. I need to point out that these crops are at the far end of the upper right corner of the image: the right side of these crops is pixels away from the image edges. This is the weakest point of any lens. And this is a 300% CROP! Please remember that. I experimented with different image blending and I think this is the best solution to see the difference in the corner, given that the right margin is the very end of the frame and a diagonal split would not have shown enough of the differences.
Just thinking about how much of a crop this is, it is amazing to see the Nokton image in the corner: there is a surprising lack of monochromatic aberrations apart from spherical and no chromatic aberrations are visible. There is more detail recorded here than in mid-frame wide open. The Sonnar is very different: wide open the corner is plainly bad. There is detail in there, but it is masked by a really hefty amount of what seems spherical aberration and lateral chromatic aberrations (LaCA). The Nokton shows a strong vignetting: look at how much darker its image is.
The Sonnar is showing a really strong level of LaCA throughout the aperture range, splitting the edges of the castle in green and magenta fringes. Detail is never high, but it definitely improves until F4. At F5.6 it loses detail again but recovers it at F8. The Nokton tells a very different story: at F2.8 the image definition is picking up noticeably and the contrast levels go up a notch. The faint traces of LaCA appearing as the spherical aberration goes away are irrelevant. The corners peak at F4 and look excellent, with the same amount of detail as the rest of the frame. That is a really incredible corner performance.
Let’s see all the shots together with the centre to corner progression per each aperture:
The Voigtlander Nokton 50mm 1.5 II VM is a modern lens, and it happens to have amazing corner performance. The mid-frame drop is seen even on much more expensive aspherical lenses (look at the same test in my big 50mm lenses comparison: the Leica Summilux-M 50mm 1.4 ASPH does the same), but the detail is fully recorded even in mid-frame from F4. Some online reviews state that the Nokton II does not well at infinity. These are 300% crops and it rocks. What are they shooting?
The Zeiss C Sonnar T* 50mm 1.5 ZM doesn’t perform anywhere near the levels of the Nokton. It is a 1932 design and it shows, even if slightly modified for modern times. While pretty sharp wide open in the centre it gets pretty fuzzy from F2.8 to F5.6, getting better again at F8. The mid-frame gets decent at F5.6, and it’s not a field curvature dip, it’s a gradual deterioration of the image off axis. The corners are just a bit nasty.
Let’s look at the Minimum Focusing Distance and magnification: the Nokton has a MFD of 0.7m, which might not sound great but it’s standard in the rangefinder world. The actual rangefinder mechanism doesn’t go closer than 0.7m because of parallax issues. The Sonnar has a MFD of 0.9m, which is not great even in the rangefinder world.
The subject of the test is a camera battery measuring 55x37mm. I carefully refocused the lens for each shot to avoid possible focus shift issues, which we will examine later. The first image is the full frame, followed by 100% crops.
The magnification is dramatically different, those 20cm on MFD do make quite a difference. Wide open the Nokton shows uncorrected spherical aberration (unavoidable for a well balanced lens without a floating lens group/element, aka FLE, to correct for the close distance aberrations) but also green-magenta fringing caused by longitudinal chromatic aberration (LoCA). At F2 it seems that we are looking at a different lens, with plenty of detail and no spherical aberration, no LoCA. From F2.8 the image is tack sharp and the quality peaks at F4, where it’s spectacular.
Wide open the Sonnar is not particularly sharp and there is an inordinate amount of longitudinal chromatic aberration (LoCA), tinging every detail with red and blue. At F2 the LoCA has been brought to heel but the definition is not crisp. At F2.8 the detail is definitely improving, although there is a slight red LoCA fringing all over it. F4 is starting to look really good, the peak is at F5.6 before some diffraction creeps in at F8.
Neither lens does perform incredibly well wide open, but from F2 and even more F2.8 the Nokton is showing off. The Sonnar is not even close, but stopped down to F5.6 it is capable of good definition at MFD. Unfortunately that performance will not be available without live view at such distance because of its focus shift. Let’s have a look at that:
Focus shift
Focus shift is inherent in optical devices using spherical lenses. It is caused by the unavoidable spherical aberration. To understand more please refer to this article. It can be mitigated with a FLE, which the Nokton and the Sonnar lack, but is found on the Leica Summilux 50mm 1.4 ASPH for example. This means that our two fast prime lenses will have focus shift. No question. But how much of it? Is is relevant in real use? Let’s have a look!
The two tests were run at the same time, on the tripod and without moving the camera, one lens after the other: the Sonnar has a slightly longer focal length (46 degrees angle of view versus 46.3 degrees for the Nokton). But is a difference of 0.3mm that visible? It seems so!
Starting with the Voigtlander Nokton 50mm 1.5 II VM, we can see that focus shift is minimal. The target never loses sharpness, although at F2.8 and F4 it finds itself at the margin of the depth of field (DOF) while remaining sharp and defined. At F2 there is no noticeable shift. At F5.6 the DOF is expanding towards the lens again. Spherochromatism (SC), the out of focus colour shift due to longitudinal chromatic aberrations (LoCA) and visible as green beyond and magenta in front of the plane of focus, is certainly visible from wide open to F2.8. It disappears from F4.
The Zeiss C Sonnar T* 50mm 1.5 ZM is a different animal altogether. Wide open we can see a hefty amount of uncorrected spherical aberration making the out of focus details behind the plane of focus still quite well defined within the spherical blur: the lines and numbers should be totally blurred at the further end of the focusing calibration device, but they are really well defined with a “glow”around them. Also, there is a moderate amount of spherochromatism.
Any focus shift? You bet! At F2 the focus plane has already moved backwards by 2cm. That is a massive amount of focus shift for just one stop from wide open! The target is already losing definition because it is already outside of the depth of field (DoF). At F2.8 the focus plane is 4cm beyond the target, which is now quite fuzzy. At F4 we are in la-la-land. The plane of focus is outside the focusing calibration device, the acceptable sharpness DoF starts more than 3cm beyond the intended target. At F5.6 the DoF keeps on getting deeper but it barely manages to reach backwards a little, starting now almost 2cm beyond target. At F8 the target is finally getting sharper again, falling just at the edge of the acceptable sharpness DoF.
Overall focus shift is present but not a real issue with the Nokton: it can be noticed only when you are shooting detail at MFD and F2.8 or F4 and rock back and forth with your breathing. There is no leeway if you rock forward. If you stay still the subject will be sharp. The Sonnar is showing that its reputation about being terrible for focus shift is wholly deserved. It is terrible. I have no idea why anybody would want to put up with it if using it as a general purpose lens.
Coma, astigmatism and sunstars
This test shows the upper left corner of both lenses. The Sonnar image is flipped to show them side to side. Coma and astigmatism are monochromatic aberrations, we will see chromatic aberrations as well here but analyse them in more depth in the dedicated test.
The difference is quite striking wide open, but gets really irrelevant by F2.8.
Wide open the Nokton is already showing off: we can detect a little external coma, traces of tangential astigmatism and a little green fringing from LoCA, but already a high quality image. At F2 only a trace of LoCA remains, and from F2.8 it is just impeccable. The sunstars start appearing already at F2 thanks to the 12 straight aperture blades, and are defined and beautiful from F2.8.
The Sonnar wide open shows external coma and severe sagittal astigmatism (SA) combining to create the dragonfly shapes towards the corner where the points of light should be. LaCA is also heavily fringing those “wings” with blue and the outward margins of the highlights with yellow/orange. Stopping down to F2 improves the image dramatically, bringing the SA almost completely under control in most of the frame and reducing the comatic aberration to insignificant levels. At F2.8 both chromatic and monochromatic aberrations are really well controlled and some sunstars are blossoming from the highlights. They are less defined than on the Nokton but they get similar from F5.6 and at F8 they are distinguishable only if you count the points, that are 10 instead of 12. Irrelevant: they look great in both cases.
Overall I would say that the monochromatic aberrations differences are significant but only wide open and one stop down. Again, the Nokton is the better lens.
Chromatic aberrations
We will be looking at LoCA, LaCA (lateral chromatic aberrations) and purple fringing, either optical or digital. What is the difference, you might ask? The most common form of purple fringing (PF), seen in high contrast transitions like branches or leaves against a very bright sky, is caused by a secondary spectrum purple colour that is focused in front of the other colours and is not well corrected even in apochromatic designs. The digital PF (DPF) is caused in the same high contrast transitions but it seems to be a digital sensor dependent artefact, caused by the bright light spilling into neighbouring micro lenses and sensels, thus producing a pink-purple fringe.
The first series shows centre crops of a big fence:
The Voigtlander Nokton 50mm 1.5 II VM shows traces of DPF and a hint of PF in the area of highest contrast wide open. The PF disappears at F2.8, the DPF needs F5.6 to be almost invisible. This is a great performance overall, with no LaCA or LoCA disturbing the central part of the image.
The Zeiss C Sonnar T* 50mm 1.5 ZM doesn’t perform as well. Wide open there is pervasive PF over all details, degrading completely the image. At F2 the PF is brought under control enough to see that the silhouetted fence should be black, but now all dark detail is fringed in red, caused by LoCA. At F2.8 the PF seems to be gone, only the red fringing remains. At F5.6 and F8 the fence is quite well defined and the red fringing almost disappears, but just off centre we can see some LaCA appearing with blue-red fringes.
Corner:
In the Nokton images there is a small amount of green-purple LaCA fringing throughout the aperture range but it’s barely visible and you have to be looking for it. The worst chromatic aberration is some bluish fringing in the very far edge/corner, but it’s such a small area to become irrelevant.
The corner in the Sonnar shows what happens when you throw a healthy amount of LaCA, LoCA, PF, SA, spherical aberration, coma and possibly salt and pepper in the same image: not a great look. Stopping down the aperture the image clears up quite a bit starting from the mid-frame, but still leaving a lot of aberrations in the corner. PF goes away in the corner only at F5.6. At F8 the sharpness is pretty good all the way into the last pixels. But: as soon as some detail appears (mid-frame area, from F2.8 onwards), we can detect a strong blue-red LaCA fringing that never leaves the image.
Again, there is no doubt about which is the better lens technically. The Nokton is miles ahead in the chromatic aberrations control. This shouldn’t come as a surprise: it’s 90 years younger!
Flare handling
The series is taken wide open to get the worst case scenarios. The source of light is a LED powerful torch, shone straight into the lens, then obliquely around 45 degrees, then at almost 90 degrees. I repeat: these are worst case scenarios!
The flare resistance of the Nokton is exceptional apart from one instance: when the light source is hitting the lens elements obliquely from outside of the frame. This is a weak point for most lenses, but the blooming is quite prominent.
The Sonnar doesn’t quite reach the levels of the Nokton in flare resistance, but I find it to be exceptional for such an old design: apart from the goodness of the optical cell I think a lot of this performance is owed to the quality of the Zeiss T* lens coatings. The Sonnar mostly suffers from flare in two instances: straight on, light shining in the lens centre, and when the light source is hitting the lens elements obliquely in the outer image circle and from outside of the frame like on the Nokton. Great performance overall for an almost 90 years old lady!
Once again the youngster shows that technology advancement helps a lot, but the older generations still hold their own.
Vignetting and distortion
Let’s compare them first:
The Nokton vignettes a lot. This amount of vignetting can definitely be obnoxious when wide open. I certainly noticed it in some pictures and wanted to compensate for it: I generally never feel the need to with any lens. I guess the strong vignetting might be due to the tiny size of the lens coupled with the fairly small filter ring diameter of 43mm. The optical design and the slightly bigger filter ring (46mm) might account for the more moderate amount of vignetting of the Sonnar. Let’s see how much of a difference it does really make seeing them side to side:
Looking at it this way the difference seems less striking, but I have noticed it in use and it is a consideration to keep in mind especially for film shooters. The Sonnar fares a lot better than the Nokton with vignetting.
And it does also for distortion:
While the Nokton has a moderate amount of pincushion distortion that I rarely ever noticed, the Sonnar has almost no distortion, apart from a slight barrel bend towards the very corners. A minimal correction solves it, but I don’t think it is really needed.
Ladies and gentlemen, the bokeh!
Bokeh tends to be a very fashionable subject, and it is, in my opinion, a vastly overrated characteristic of a lens. It can be more or less smooth, it can be a bit nervous or wiry, outlined, colour fringed, but it is still the unfocused area of the image. We are supposed to put something interesting as a subject in that image, so the quality of the bokeh really shouldn’t matter. But alas, the bokeh debate is heated indeed, and a lot of amateur photographers seem to be obsessed with its quality (as in mix of characteristics). There seems to be no bokeh quality that is commonly understood as good, opinions are varied and personal. I will analyse the bokeh for its unobtrusiveness: while the various peculiarities of the bokeh can be subjectively pleasant or unpleasant to see, the smoothness and neutrality of it is something we can assess and take as the desirable character (or lack thereof!). From there one can judge if the less smooth bokeh is something they like and aspire to. For me, unless it really jars the eye and distracts, it doesn’t make much of a difference. But the smoother the better if I have to choose.
In the case of the Zeiss C Sonnar T* 50mm 1.5 ZM the bokeh seems to be one of the qualities that give it its cult status. In the 50mm lens comparison the Voigtlander Nokton 50mm 1.5 II VM was one of the best performers for the bokeh rendition test. How do they compare directly?
Bokeh at close focus and points of light
Here is the full frame:
Now a crop of the image, side to side, with the Sonnar image flipped for direct comparison:
Wide open the Nokton shows a little outlining and visible green spherochromatism (SC) around the out of focus highlights (OOFH). The off axis OOFH show a strong tendency towards what is commonly referred to as cat’s eye bokeh (CEB), the rugby ball shaped OOFH, most likely due to the prominent mechanical vignetting caused by the small filter ring. The Nokton bokeh is exceptional for the fact that it has no onion ring bokeh at all even though it is an aspherical design. In fact, its OOFH look like those of a spherical design. Fantastic. As soon as the aperture is stopped down the OOFH take on a polygonal, 12 sided shape due to the straight bladed aperture mechanism design. The SC and mild outlining are gone by F4.
The Sonnar 1.5 shows a very strong yellow and blue outlining in the medium brightness OOFH, consistent with its LaCA. The outlining is just yellow on the brightest ones. Spherochromatism appears from mid-frame as a green fringe on the edge of the OOFH pointing to the image axis. CEB is not pronounced, becoming a cylindrical shape in the corner. At F2 there is a noticeable improvement on the outlining issue. A faint circular saw blade shape is appearing due to the inwardly curved aperture blades. The outlining has disappeared at F2.8 and from F5.6 the OOFH are starting to produce a sunburst like the Nokton ones do.
Overall both lenses have strengths and weaknesses on their bokeh: the weaker points are the CEB and SC for the Nokton, the strong LaCA and outlining for the Sonnar. In my opinion neither rendering has any influence whatsoever on the contents of a well made image.
Bokeh at 3m
The character of the bokeh can change considerably with the distance from the subject and from the background and their relative distance. See how much that can be true in the TTArtisan 50mm 0.95 review here. First, the full frame:
Now the relative crops to better see it, with the Sonnar images flipped:
The wide open bokeh of the Nokton appears very smooth and shows no outlining. The SC is mild and doesn’t influence the rendering. There is a hint of swirling, most likely due to the pronounced cat’s eye bokeh of this lens. At F2 the bokeh is still smooth and the swirling has almost disappeared. At F2.8 the swirl is no more and the image remains absolutely neutral in the defocused areas till F8, at which point it becomes difficult to see any bokeh!
The Sonnar wide open bokeh is fairly smooth and quite pleasant, notwithstanding a slight outlining lending a hint of wiriness to some areas. The SC is present but does not degrade the image unless you pixel-peep. At F2 it becomes just smooth and it remains so when stopping down. There is a little higher sharpness in the corners for both lenses.
The differences in bokeh rendering at this distance are so insignificant that I see no reason to choose one or the other only for the bokeh character. The real difference is the sharpness and aberration free detail of the subject.
Bokeh at 6m
Same as before, full image and then crops:
Comparison crops. This time the Nokton images have been flipped:
The Nokton shows a smooth background from wide open again, no change in the bokeh character with the subject and background distances. It is a lens with a reliable rendering. SC is still present and prominent if we pixel-peep but irrelevant in the actual image. The corners are quite sharp, showing some negative field curvature at this focus distance. From F2 it becomes futile to talk about bokeh anymore, it is barely visible although still smooth.
If we pixel-peep the Sonnar OOFH are showing some outlining at this distance and some purple colouring inside caused by the spherochromatism, that is also tinging the branches against the sky with green. This is the same as the focus at 3m but slightly more noticeable here. I need to point out that every single lens in the 50mm lens comparison here does the same. Like in the Nokton images the corners seem to be sharper than the centre.
The bokeh from this mythical Sonnar design is…nice. Nothing exceptional there in my eyes. When we compare it to the Voigtlander Nokton 50mm 1.5 II VM the differences are so superficial that I don’t really see a reason to call the Sonnar bokeh particularly special.
Bokeh at MFD
I will add an extra test for distant background and the lens focused at MFD:
The Sonnar is hindered by its longer MFD, getting less background blur. The Nokton wide open produces a complete wipeout of the background, smooth and creamy, while the Sonnar shows some outlining that, with the less defocused effect, produces some wiriness and shapes in the bokeh (outlining of lighter branches on bottom right). Stopping down the Nokton remains smooth. It looks like the Nokton might be one stop ahead of the Sonnar in the amount of defocusing thanks to those 20cm of MFD advantage. Even cross checking at one stop difference the Nokton is still smoother at F2.8 than the Sonnar at F2, then we are getting even. Overall for me this is a big plus for the Nokton.
Portrait
If you speak to any fan of the Zeiss C Sonnar T* 50mm 1.5 ZM they will describe semi-divine qualities, but mostly they will mention the heavenly bokeh and how it imbues magical properties into any portrait. How true is that? What I have seen about the bokeh hasn’t given me any spiritual experience. Will I be enlightened with the portraits?
I set up a studio-like kind of portrait with a light 45 degrees angle to the right and above the subject, my beautiful wife Daniela. There was a reflector on her left to lift the shadows. No rim light around the hair because I could not produce a decent one with my extremely limited lighting equipment.
I will show the portrait side to side wide open because there is hardly a difference at this viewing distance, then I’ll get close to show the eyes and any rendering difference.
Can you see a difference this way? I can’t unless I press my nose against the screen.
Let’s see some close-ups:
If you notice that Daniela is not smiling much it’s because this series is a small part of a much bigger one shot in the same session for the big 50mm Leica M lens comparison: she couldn’t keep the smile for such a long time! She was being patient throughout a very long session. I used the electronic viewfinder (EVF) to focus each shot precisely.
The wide open first shot with the Nokton is mis-focused, the focus plane is slightly behind the closest eye (probably due to the egregious shutter-lag of the Leica M240 when shot in live view/EVF mode: her breathing could have moved her head back a fraction while the camera was debating on when to shoot after I pressed the shutter!). This doesn’t detract from the usefulness of the image. The uncorrected spherical aberration is softening the image slightly, but already from F2 the eyelashes and eyes are sharp and the image is “sparkling”, with a beautiful rendering. From F4 the detail is razor-sharp.
Wide open the Sonnar is not tack sharp but there is plenty of detail. Aficionados of the Sonnar talk about the lower sharpness as an asset because it can make the skin blemishes and wrinkles softer and less harsh. I don’t see that making a big difference in this portrait, the recorded detail is still high. There is a gentle transition to the out of focus region, visible on Daniela’s right eye, eyebrow and cheek (on our left). At F2 the detail is already very sharp, and it peaks at F2.8. It makes no sense to go beyond F4, the quality of the image is already stunning.
Keep in mind that each shot has been carefully focused through the EVF and focus peaking. When using the Sonnar this level of accuracy is impossible with the rangefinder at this distance unless you are wide open. As soon as you stop down you are guessing where the plane of focus will fall, thanks to the spectacular levels of focus shift.
Let’s see another couple of shots outdoors, using the rangefinder to focus. Can you guess which lens was used in each shot? These are straight out of camera, no post-processing done at all:
When you look at these portraits you realise how little difference it makes what background defocus you have. That’s not where the eye falls, any non-photographer viewer will look at the subject, not analyse the bokeh. Only us photographers-nerdy-geeks will scrutinise the bokeh.
Conclusions
The Voigtlander Nokton 50mm 1.5 II VM and the Zeiss C Sonnar T* 50mm 1.5 ZM are two different lenses. They look almost the same from the outside and are very similar on the spec sheet, and they have a fairly similar price. But the optical performance is quite different.
Let’s start with the pros and cons of the Nokton:
PROS
Great handling, small and a pleasure to use
Good performance at infinity
Fantastic performance at MFD from F2
Really well controlled focus shift
Great coma and astigmatism control
Outstanding chromatic aberration handling
Excellent flare performance overall
Beautiful sunstars
Soft and beautiful bokeh
Great choice for portrait work
CONS
Vignetting is obtrusive
Spherical aberration wide open at close distance
Flare with sun outside of frame
That little niggle with the lens mount alignment mark
The balance is very much on the pros. It surely is a good lens.
What about the Sonnar?
PROS
Fantastic handling, small and a pleasure to use
Beautiful sunstars
Low vignetting
Minimal distortion
Flare control
Good bokeh
Great choice for portrait work
CONS
Infinity performance is poor
MFD is not great
Terrible focus shift
Poor coma and astigmatism control
Flare with sun outside the frame
Intrusive chromatic aberrations
Quite pricey for the performance
The balance between pros and cons is different for the Sonnar.
Let’s draw some conclusions.
How will I evaluate these two fast prime lenses?
My preferences in photographic equipment are these: first of all, the camera and lens have to disappear in use. What do I mean by that? If you have to fumble with the equipment because of ergonomical issues, fight it for the same reasons (see here) or be mindful of its optical/performance flaws while you are shooting to avoid missed focus/unusable images, then that equipment is not for me. I want to just think about making a photograph when I am behind the camera, the equipment should just do its job to allow me to get what I want easily and without hesitation. Secondly, I don’t want to have multiple lenses in the same focal length: I just want one to work with any subject. If I choose to use a 50mm lens I don’t want “options”, one is enough. One that works flawlessly for me.
No lens can be perfect optically. Normally the more well corrected the lens is, the more lens elements in the design and the larger it is. The Voigtlander Nokton 50mm 1.5 II VM goes the opposite way and becomes the smallest production lens for full frame at that speed, while maintaining an incredibly high imaging performance. That is impressive.
The price of £849 for the aluminium version and £899 for the nickel brass version might seem a lot outside of the rangefinder world, but in the Leica M system it is an absolute bargain given the performance.
The Voigtlander Nokton 50mm 1.5 II VM is a beautiful lens and it definitely disappears in use. You just shoot and trust the reliable results from it. It could be the only 50mm lens you will ever need. It has found a stable place in my camera bag. Actually, it almost never leaves the camera itself! I highly recommend it.
The Zeiss C Sonnar T* 50mm 1.5 ZM, on the other hand, won’t disappear in use: you always have to keep in mind that you have to compensate for its flaws. That’s a straight no-no for me for everyday use. Also, the image quality is not good enough for me. In my mind this kind of lens is nice for playing around and enjoying a sort of Holga kind of experience for the images it delivers. I know this will “offend” the Sonnar fans, but that’s how I see it. It is a bit soft, it has a real focus shift problem, it never delivers really high image quality (apart from the portraits to be fair. But that makes it a one trick pony!): I have no use for such lens. I want a fast prime lens to reliably deliver high quality images without having to wrestle them out of it. The Sonnar is not that lens.
I am perfectly aware that this negative view won’t sit well with the Sonnar aficionados, and that’s ok. It is just that: an opinion! The amount of glowing reviews on the net and the passion with which this lens rendering is described by those who like it is a testament to the fact that there is a market for the Zeiss C Sonnar T* 50mm 1.5 ZM and it is a very appreciated optic. Just not by me.
So, who is this lens for really? Should you buy it?
I think this lens can deliver really beautiful images in real life shooting. It is also capable of recording good detail wide open. But overall you get this lens for its specific look, which could be defined as vintage. Do I want the vintage look? No, I consider it a gimmick. For you? It might just be what you were looking for. If that’s the case, go get it now. It is a pleasure to use. The price, albeit hefty, is still quite low in the Leica M realm: £919.
So, which one to choose?
If you are looking for a modern, reliable, versatile and high performance fast prime 50mm lens buy the Voigtlander Nokton 50mm 1.5 II VM. If you are looking for a more vintage look and don’t mind taming the lens, get the Zeiss C Sonnar T* 50mm 1.5 ZM.
Where I see the Sonnar having a much better chance of being a versatile choice is shooting film. The focus shift issue will be a lot less noticeable and the film grain and character can blend very well with the lens rendering.
I will show another few side to side and split sample images. Notice how hard it is to distinguish them at first sight if you don’t read the labeling! Only us geeks analysing the bokeh will recognise the differences!
By the way, if you are still wondering about which lens shot which portraits above, they are: Sonnar, Nokton, Nokton, Sonnar.
Please let me know what you think in the comments!