MS-Optical 50mm f/1.1 Sonnetar: magic time

The MS Optical Research Sonnetar is like The Life Aquatic with Steve Zissou. You either get it or you don’t, and if you don’t understand Jacques Cousteau, Willem Dafoe playing a subservient gay German, or Wes Anderson in general, there is no one who can make you like it. By the same token, if you drive Jaguars, no one with a 276hp front-drive Camry is ever going to win you over by telling you it has a higher thrust-to-weight ratio than an XJS V12 with the flying buttress hard top.

You don’t buy a Sonnetar as your only 50mm lens; in fact, you don’t even buy it as your only fast 50mm lens (and by the way, 50s should either be fast or fun – there is nothing more bland than a 50mm Summicron). The Sonnetar has strange controls for most (the rotating front barrel is exactly like using a Contax or Nikon rangefinder). It vignettes like crazy. At any distance, you can have your choice between correct focus and optical correction.

Why would anyone like it? It’s actually a big question whose only easy answer might be that when you have to shoot an f/1.1 lens in ultra-low light conditions, you pick your poison. You’re playing the limits.

N.B. All pictures shot in b/w are shot with a new Leica Monochrom (typ 246). All shots in color are with an M (typ 240). It’s absurd to change color pictures to monochrome to try to judge sharpness.

What is it? The MS-Sonnetar is the second modern revival of the 50mm f/1.5 Carl Zeiss Sonnar (West Germany, 1950s-1960s), the first one being the Zeiss ZM C-Sonnar 1.5/50mm. Why this type of lens is popular today is puzzling; when lens coatings enabled highly corrected 50mm lenses like the Planar, all of the expensive cemented groups of the f/1.5 Sonnar became obsolete. Today, the popularity of the Sonnar pattern might be in its imperfection: focus falloff in the form of field curvature and vignetting. The Sonnar yields marginally smaller and lighter overall packaging than a Planar or Double Guass, and it has slightly higher resistance to flare.

Every Sonnar revival/clone/ripoff over the past 50+ years has had its own set of strengths and weaknesses; it seems that almost none of them shows the balanced performance of the original Zeiss design. They either sacrifice sharpness for bokeh or go gaga for bokeh and live with a lot of focus shift.

The Sonnetar goes for the gusto with fewer elements and only one cemented group; a lighter, more compact barrel; and almost an entire stop of extra speed. It is the fastest Sonnar-style production lens in terms of T-stops, edging out the 50/1.1 Zunow by virtue of having fewer elements and more effective coatings.

Getting a handle on it. The Sonnetar is a very compact lens; the barrel is smaller than a 50mm Summicron, flaring out to a wider front section that takes 52mm filters (and no, full-sized B+Ws do not vignette). It’s hard to say whether it is modeled after a Zunow, a 50/1.1 Nikkor, or an Opton Sonnar. But all of them have a particular shape to them. The Sonnetar looks most like the Zunow, with the focusing and aperture rings reversed.

The frontmost ring is focus (supplemented with a small lever in the back if that’s what you want); the rearward ring is the aperture control, which smoothly adjusts from f/1.1 to f/16. Like a lot of older lenses, as the aperture numbers get higher, they get closer together (it is probably also a side effect of the Sonnetar’s super-nifty, perfectly circular German iris. But no matter in splitting hairs between f/11 and 16; you won’t be shooting there anyway.

The tough part of the ergonomics is something you’d never expect: the rear lens cap. It screws into the rear lens group, which unfortunately is also the thing that is the coma control. As for the front cap (which also screws in), you’ll probably leave that in the box with the hand-drawn spherical aberration measurements and the pretty hood. You’ll either use an MRC filter or a pinch cap to keep your fingers off the front glass.

Overall build quality. Done out in matte black chrome, the finish of the Sonnetar is a good match for a black Leica M-P or Monochrom typ 246. The black anodized finish is very tough, and the mounting ridges that you grasp to mount the lens will take bits of skin along with them. Numbers are clearly engraved and filled in white. They are legible and inoffensive. There is no way to 6-bit code this lens, since the rear flange is integral with the lens barrel (it is very much built like an old rangefinder lens with a rotating optical unit).

The glass (modified Sonnar design, more air-spaced) is perfectly clean and perfectly coated (from what I understand, MS Optical’s multicoating is a simple 2-layer). The reality is that the efficiency of modern coatings and the low element count makes internal flare a non-issue. Interior blacking is actually dark grey, which may seem puzzling, but if it’s good enough for telescopes, it’s probably good enough for camera lenses.

There are some build quality nits. One is that the lens (both on the sensor and in the rangefinder) hits infinity with about a mm of travel left in the focusing ring. This is probably an artifact of having that ring be the same part that provides the rangefinder cam. This might be of concern if you are trying to focus at infinity by feeling for a stop – and it is no different a problem than using an Asian LTM adapter that is a fraction of a millimeter too thin. It almost seems like you could just loosen the focusing ring screws and shift it so that infinity was on the stop

The other is that MS-Optical only uses a couple of actual lens mounts. The 51.6mm lens mount provides cam action that approximates a 51.6mm (Leica-spec) lens. Its frameline selection is determined by whether the mount is compressed around a notch in one of the bayonets or not. This lens uses about 90 degrees to go from 1m to ∞, which is quite short. This gives you a much faster acquisition time for focus but degrades the focus accuracy. Contrast this to 1950s and 1960s LTM lenses (and indeed the 75 Summilux), whose ponderously slow focusing rate can cause you to miss the moment completely. In any case, you are much better off using the ring than the lever because the larger diameter of the barrel provides better precision (because it takes more movement of the control surface per unit of focus change).

The $&@(!#% “coma adjuster.” The most famous feature of this lens is a “coma adjuster,” a ring around the rear element that has a white indicator dot and four distance dots (1m – white; 2m – white, 4m – red, and infinity-white). The lens is sold with an instruction sheet that tells you this is for adjusting “coma,” which would be the shape of point light sources (round or not). Why does anyone care about coma? It’s a big deal for telescopes, and that’s what Miyazaki designed for most of his life. What you get in terms of optical performance in the near range is a set of very subtle changes. Perhaps this operates better at a distance, but for its stated purpose, the adjuster seems a little bit gimmicky.

What is not so subtle is that the same control – determining the position of the rear lens group – has a tremendous effect on focus (because it changes the focal length of the lens) and on field curvature (whether the plane of focus is flat across the field or curved inward at the edges). This almost off-label use is actually very easy to exploit (see the discussion of what the directions actually say below).

Focal length control is very important on a super-speed lens. A Leica rangefinder assumes the same movement as a 51.6mm lens. Nominal “50mm” lenses that have a 51.6mm focal length can rely on simple movement of the lens cell when focusing to track from near to far at the correct rate. Shorter lenses (like 35mm lenses) have to translate a smaller amount of lens cell movement (front to back) to a relatively larger amount of rangefinder cam movement. Likewise, a 90mm lens needs the cell to move more than the cam moves. With most 50mm f/2 lenses, variances of a couple of 1/10s of a millimeter in actual focal length are not of great consequence because the lens has a little depth of field (or “fudge factor”). Lenses that have super-thin depth of field, such as an f/1.1 lens, require far more precision in their focal length to work well with a rangefinder. One can also surmise that the coma adjuster ring also serves as a calibration method for the lens that does not require reassembly.

According to the directions, this is how to use the coma adjuster ring:

Adjacent to the coma adjustment ring, you will find a white reference point (see the above illustration) to which an appropriate ring position has to be matched by rotating the ring. Using the coma adjustment system, a very high level tuning/focusing optimisation is made possible.

[…]

For Leica M Type Rangefinder Camera Users Initially, bring the red dot of the ring to the white reference point by rotating the coma adjustment ring. As you familiarise yourself to this lens, you may wish to change the ring position either to the left or right. For example, at the infinity best point, the actual focus point will be slightly brought forward (therefore, take a photo with focus point slightly backward). At the white dot that is best for 2m distance, a focus point will be slightly brought backward (therefore, take a photo with focus point slightly forward). This might take some practice and experience to achieve best results.

In real life, the tips for using this are:

• Turning the adjuster toward longer distances will make the lens focus closer to the camera.
• Turning the adjuster toward shorter distances will make the lens focus farther from the camera.
• Putting the coma adjuster on 1m will cause a back focus of 15-20cm at 1m, which is not insignificant.
• Putting the coma adjuster on ∞ will cause the lens not to focus (optically) to infinity.
• Putting the adjuster about 2mm short of the 4m mark will produce best focus at f/1.1-1.6 from just under 1m to infinity. This is not surprising, since it is a distance of about 50 focal lengths (2.5m), which is a conventional distance at which lenses are tested. It is also apparently the setting used to measure MTF (as shown on the instruction sheet).
• The lens will decouple from an M rangefinder at the minimum distance stop, so don’t do any testing below about 0.8m.

IN MOST CASES, YOU WILL ONLY BE MOVING THIS ADJUSTER 1 or 2MM FROM THE RED MARK. UNLESS YOU WANT TO GO CRAZY.

It really, really, really helps to have a LensAlign to calibrate the lens because you can see the zone of focus very correctly. Although you can trial-and-err it without this $80 plastic device, the problem is ascertaining the effect of focus shift. You want to hit a calibration where the zone of focus includes the intended point through as many apertures as you can – because like a lot of lenses in this speed class, the Sonnetar has under corrected spherical aberration that causes focus shift with aperture changes. The LensAlign lets you observe a band of high contrast as it moves (and expands) as you stop down. You don’t even need to shoot it head-on as you would with a DSLR; you need to check this from oblique angles too – because that is how you will focus your Leica in real life. Needless to say, if you are going to use this lens with a film camera, it helps to have a digital to get it dialed in.

Even within any calibration, the M viewfinder system (including the improved rangefinders for the M typ 240 and 246) has enough lash in it that the direction from which you focus – as well as small movements that don’t even produce a visible change in the RF alignment – can affect the focus point. So the word is “practice.” Wide-open, you will nudge to a slightly farther focused distance (without making the RF spot move).

Performance. All high-speed 50mm lenses (f>1.4) involve tradeoffs. The simple answer is that the Sonnetar has characteristics that vary depending on the coma adjuster setting, and these correspond pretty closely to the optimization differences in an Opton Sonnar, a 50/1.4 Nikkor LTM lens, and a 50/1.5 Canon LTM lens.

For most testing, I have kept the lens optimized at f/1.1 to 1/6 at distances up to 3m. It performs very well from 0.8 to 10m at f/1.1-1.6. If you get the calibration just right, you can keep it sharp through f/5.6, and it’s sharp across the field. At long distances, however, you get progressive blur toward the frame edges. This is gone at f/8. I suspect that the coma adjuster could overcome things, but distance shots are a little outside the use case for this lens (for distance, you are always better off with a slightly smaller aperture lens).

Sharpness seems to max out at f/1.6 (the dot between f/1.4 and f/2 on the focusing scale). Contrast is about double that at f/1.1. If something like the Canon 50mm f/1.2 LTM lens is your frame of reference, at wide-open settings, the Sonnetar is visibly better (and focuses far more accurately). If you are shooting at f/4 or smaller, something like the Canon provides much more balanced performance.

Here is a sequence that should show the differences at the wide apertures. If you click on the picture, you should be able to see it full-size. First, 0.8m, whole scene. Yes, the 44-year-old unopened bottle of Beam is real, as is the gaffe of keeping champagne at other than depressed temperatures. And no, I can’t explain the presence of the CFL bulb on the bar, since I own no fixture that takes them.

Next, check out the difference between f/1.1 (left) and f/1.6 (right) at 100%. The apertures shown in the metadata are computed by the M typ 246, so they are not entirely accurate. There is quite a bit of contrast jump in one stop.

Next, here is the same comparison at 200%. The focus point here is the stamp “Spring 1963.”

Next, here is the mid-right side at 100%. Still holding together.

Extreme left, 100%. Same story.

Real-world, stressed out, trying to get enough distance to focus in almost complete darkness, you still get good results. This is f/1.6 at ISO 2500 and 1/12 of a second:

And a bit better at 1/45 sec (by the way, the Last Word is something you ought to try sometime):

And this is the obligatory f/8 shot outdoors with a G filter.

Flare is very well controlled except in extreme side-lighting, where you can get some bizarre effects. This is a characteristic of Sonnar-type lenses. There is some “glow,” which is the normal Sonnar flare on hard dark/light interfaces that occurs when the focus point is ahead of the object. It is more visible in the preview mode of an M camera than it is in the final files. Resistance to extreme backlighting is pretty good, a lot better than with the old Canon 50/1.2:

Here is the difficult-to-replicate total flare failure mode. You might want to use a lens hood when the sun is in the corner. Or maybe not.

Vignetting is not going to be a huge issue at close distances, since the barrel is extended. At f/2 and down, it is not obnoxious, especially when combined with the automatic corner correction on the M8/9/240/246. If you want to go very heavy duty on perfect corrections, use the Adobe Flat Field plugin for Lightroom. You will need to shoot baseline calibrations at the distances and apertures you normally shoot. You can do that after the fact.

Color rendition can be a little weird. The “tantalum” glass in this lens (probably standing in for less-exciting sounding “rare earth”) shows mild versions of the color enhancing effects of a didymium enhancing filter (like a B+W 491, Tiffen Enhancing Filter, or Hoya Redhancer). Magenta and yellow seem to be favored here. Here are some pictures that should illustrate this. For your evaluation of secondary characteristics, this is at f/2:

f/4:

f/1.1:

f/1.1:

Chromatic aberration is a factor here but not in the traditional way. Wide-open, this lens tends to have the blur from adjoining colors bleed together. On an M typ 240, this looks a little bit like soft focus. On the M typ 246, this disappears completely, and the lens develops some killer contrast. This is characteristic of sticking a lot of old-school lenses on the new Monochrom body; a lot of older optical designs suddenly start looking awesome.

Bokeh is such a bourgeois concept. With spherical lenses, you either get universally good bokeh but bad focus shift (ZM C-Sonnar) or poor bokeh and reduced focus shift (50/1.4 Nikkor, 50/1.5 Canon). Unfortunately, with high-speed lenses, the latter combination (or in this case calibration) is much easier to live with. With the Sonnetar, you want to get as close to your subject as possible with as great a distance from it to the background as possible. Otherwise, you can enjoy what generation of Canon and Nikon Sonnar clones have experienced. By the way, here is a direct comparison between the bokeh of the 50/1.2 Canon and the Sonnetar. Maybe you can tell which is which?

Conclusion. If I did not currently own eleven 50mm lenses (just temporarily), I don’t know how I would feel about this one. That said, the Sonnetar is the one that seems to be welded onto my Monochrom. It’s quirky, it takes a lot of practice to use, and even after a couple of months of practice, there is still a lot to master. That said, it’s an elegant alternative to the Coke cans and second mortgages that tend to dominate the super-speed 50mm space.