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Resolution

If you expect a lens from 1950s to produce super sharp images from corner to corner at all apertures, you're probably from Mars, or Venus, or whatever other planet you like. Bottom line is that with the old optics, you should adjust your expectations - lens designers of the past did not seem to mind coming up with formulas that did not expose every freckle. Add to that manufacturing limitations and well, you get the picture. Right then... Summarit is certainly no sharpness king but I am hoping this was not your criteria when considering this lens. My personal criteria for Summarit is fairly simple - decent sharpness in the center at close and wide apertures. I don't care that much about infinity and small apertures. Why? Because pretty much any lens should perform well at infinity and stopped down to f/8 - it would be ridiculous spending a small fortune on a fast lens if your typical application does not require using a large aperture.

As you can observe from the simplified MTF50 charts below (captured by Imatest in the 1.5m to 10m focusing distances, with the best overall result plotted onto the chart), Summarit shows a subpar resolution wide open, both in the center as well as around borders. Resolution improves as we stop down the aperture and center reaches decent levels by f/2.8, while borders lag until about f/5.6. If you try to base your decision solely based on this chart, you would probably end up dismissing Summarit 50/1.4. While these resolution numbers might have been considered decent in 1950s, pretty much any modern lens would beat Summarit to pulp in this department. Furthermore, if you're using a film camera, or the full-frame M9, you should expect further degradation around image corners.

Leica M8 (10Mp)

Alas, when we look at the sample crops from the imaging target, we do not get any better impression of the lens - corners at f/1.5 are pretty blurry with basically no definition to them whatsoever. Lack of sense for image quality is exasperated by lower contrast as well, but more on that later. f/8 results, on the other hand, are quite acceptable.

Leica M8 (10Mp)

Image corners @ f/1.5 and f/8

So what should you expect from this lens in the field? Your results will probably be even slightly worse than what you've seen above, most notably at close focusing distances, due to the focus shift, which I mentioned earlier. While compensating for the focus shift is theoretically possible, in practice, it is rather hard to do so consistently because of the shallower depth of field. (An exception to the rule would be if you're using Summarit on an EVF camera like Sony NEX, in which case focus shift issues are not gonna trouble you at all) However, as you step away from the target, your results should improve, again, because of the increasing DOF (yes, DOF increases as the distance to the target increases - at f/1.5 and 1.5m focusing distance, your DOF on M8 would be ~6cm, while at the infinity it would increase to ~112m), which would cover some errors in focusing. Hence the sample crops you can find below, all shot at the infinity, look better than the ones where the the focusing target was located at 6m. I am sort of split here - as mentioned, I was hoping for a decent resolution up close, but the results do leave me wishing something more. Your satisfaction levels will differ - just don't expect a good resolution out of this lens.

Center

L.L.Corner

U.R.Corner

To give you an idea of how much performance boost you'd get when increasing the focusing distance, I plotted MTF50 results averaged at various distances to the target. That is, a point at 1.5m is an average of MTF50 results measured in two areas - image center and image borders, and at all aperture levels. Notice the significant boost in the chart as you move towards 10m. Of course, there's more to the lens than just sharpness, so read on...

Color & Rendering

Over the last few months that I have been using Summarit 50/1.5 on my M8, the lens has become an endless topic of my grumbling. I swear that the lens was designed by some mad genius who wanted only the most patient to succeed. The lens is 80% frustration and 20% magic, meaning that 80% of results I'd get are throw-away, but the remainder are absolutely fantastic. While I am still actively evaluating this lens (jumping ahead, I think I'd like to keep it), a few patterns seems to be shared with its slower Summarit version, which I owned for some time now. Firstly, the lens is a low contrast lens - from its widest aperture to about f/4, the lens renders images that are rich in grey tone gradations, but low on overall contrast throughout the frame. But, what is interesting about Summarit, is its 'gentlness' in subduing contrast - while the dynamic range of the raw data is not as good as with more capable modern lenses, Summarit's emphasis on mid-tones and shadows, gives you a good chance of recovering contrast without destroying much of the overall image detail. The resulting images might not look super-contrasty even after the recovery (unless of course you decide to disregard data loss and crank up contrasts to the max), but have enough contrast so not to look washed out. This is particularly true for portraits, where lower contrast lenses tend to go easier on skin tones and help create lighter feel to portraits.

ISO 160, 1/90, f/1.5, 50mm (Leica M8)

Because of the lower global contrast, Summarit also mutes its color palette quite noticeably. Granted, the richness of the color really depends on a gazillion number of other factors, but what I noticed is that in environments with even or low levels of illumination, Summarit performs quite well, giving a balanced, albeit subdued palette, often rich in light blues, yellows and other pastel/warmer hues. Boosting contrast by either re-leveling the histogram or adjusting curves typically gives very good results.

Much has been discussed about the so-called 'Leica glow' of the old Leica lenses. Community seems to be split about this - some people love it others don't and once thing is certain - nobody seems to be able to describe what exactly it is and why is it present in photos. I am no expert on this subject and can only speculate that by 'Leica glow' many refer to the spherical aberration which adds some 'haziness' to the picture at wider apertures. Add some light bleeding due to halation and you get images that that have this feel of glow to them. Of course some Leica users might argue that this Leica glow is quite unique and cannot be simply explained by halation or spherical aberration. But, I think many older lenses, including non-Leica designs, exibit this characteristic - Xenon for one has it and it was not designed by Leica. Original Contax Sonnar 50/1.5 has it as well. Carl Zeiss even tried to recreate this feel in its modern Sonnar 50/1.5 version, although I think they could have achieved better results by single coating the lens to make the lens a bit more prone to light flare, which also hazes pictures. Anyhow, the resulting images are certainly unique and whether you like this after-effect will ultimately dictate your preference towards lenses Summarit. Personally, I am not a huge fan of such look, but do think that having a lens capable of giving you this 'gloawing' for those especially-creative moments is probably warranted. But my preference would be to use such a lens in B&W photography, where spherical aberration is actually more pleasing to my eye.

But given that the lens produces lower overall contrast in images, Summarit 50/1.5 also manages to handle lateral chromatic aberration fairly well. The chart below summarizes Imatest results that the lens delivered. You can observe that CA never exceeds  0.6px, even in extreme corners, which by all means is not very high. Of course, the visual aspects of lateral chromatic aberration can vary quite significantly from the results measured in controlled environment, but throughout my tests, I have not seen any serious sign of CA that would have required me to do some post-processing to reduce its impact.

Leica M8 (10Mp)

DOF & Bokeh

Many users of the older Leica lenses, including Summarit 50/1.5, claim that these lenses exibit the so called 'swirly' bokeh. It is hard for me to generalize Summarit's bokeh though - while the lens certainly showcases bokeh that has some double-edging as well as some longitudinal CA, which contribute to the 'swirliness' feel of Summarit's bokeh, the extent really depends on three main factors - focusing distance, background and aperture used. I have had great success with this lens shooting against not-too-busy backgrounds when the bokeh did not even showcase any swirly elements, while other shots with random and excessive background elements and lightning would turn the background into a 'Picasso-esque' mask. This is a prime example of 'one size does not fit all' when the same lens can behave quite differently under varying conditions. But if you wanted consistency, you would not have picked up Summarit, right?

Despite its age, Summarit does not really provide much tradeoffs when compared to the bulk of fast 50mm lenses, modern or old alike. Low contrast at wide apertures really means that you need to play with the resulting images in Photoshop to make the subjects stand out. It's doable, but if the so called 3D-iness of the subject is your primary criteria (which is typically possible with lenses that generate high local contrast and low global contrast along with reasonably high center resolution, none of which Summarit provides), than you should look elsewhere. Summarit excels in situations where you need to soften the scene, create lighter feel or even a 'paint-over' effect where the subject almost blends into the background. Summarit does not master harsher lighting well and so if your background has some strong highlights, you are likely to end up with some not particularly pretty 'smudges'. The relationship between the external factors and the quality of bokeh you end up with is fairly complex and I don't feel I have experienced everything that Summarit can or cannot do at the moment of this writing, so my advice to you is to experiment - if you have some doubts about whether you might or might not like the outcome, you should probably skip Summarit and go for a 'no brainer' lens.

The series of shots below demonstrate what bokeh can look like when shooting at MFD and medium focusing distances, while the bulk of the background is located at infinity (about 15m to the tents seen in the pic and over 50m to the building in the background). The main limiting factor of the Summarit, like with pretty much any other lens of this period, is its MFD - at ~1m, it is not the shortest in the class and hence imposes some limitations on the shallowness of DOF. The character of bokeh here is fairly standard - I don't see any swirliness that we discussed earlier. The background is blurred quite nicely at wider apertures and short focusing distances. I boosted the color palette a little bit by readjusting histogram levels to increase contrast a bit and adding a little bit saturation.

DOF @ 1m

DOF @ 3m

I will close this section with the now traditional shot of the porcelain cat, done at the MFD. The picture has not gone through any post-processing and exemplifies what you'd right out of camera. Nothing really stands out in this shot, and you don't get a good sense of isolation. The feel is very representative of other lenses from the same era - Summitar and collapsible Summicron - if you liked the bokeh rendering style of these lenses that you would also like the rendering of Summarit.

ISO 320, 1/350, f/1.5, 50mm (Leica M8)