Home Cameras/Lenses Leica Review: Leica APO-Summicron-SL 50mm f/2 ASPH

Review: Leica APO-Summicron-SL 50mm f/2 ASPH



This will be a short report. Beyond the obvious superlatives there really isn’t that much to say about this wonderful new lens.

The 50mm is the fourth lens in the APO SL Summicron lineup. The wide-angle lenses are promised for 2021, while the 75, 90, and 35mm have already been released.

With the Leica SL
With the Leica SL

The Lens

I had an early prototype of the 50 with me while testing the 35 APO SL early in the year. I took it to China on a trip to Hangzhou.

Later on, during May and June, I had a final prototype lens which I used to shoot a couple of weddings and a trip to Cornwall.

With the Leica CL
With the Leica CL

As expected, the APO-Summicron-SL 50 f/2 Asph is exactly the same form factor as the previous APO Summicrons — and the future ones as well. The optical design varies between the lenses: In this case it is twelve elements in ten groups with three aspherical lenses and four aspherical surfaces.

With the Panasonic S1
With the Panasonic S1

So far, all the lenses support a 1:5 magnification ratio, which is pretty useful. For the 50mm, this represents a closest focus distance of 0.35 metres.

The lens weighs in at 740g, not light perhaps, but it does balance perfectly on the SL (and the Lumix S1) and is easy to handle for a full day’s shooting. Perhaps it’s worth bearing in mind that the Leica 50 Summilux SL is 1,065g and the Lumix equivalent is 995g.

It was with real regret that I handed the lens back to Leica on a trip to Wetzlar early in July.

After testing the 35 APO, I had managed to resist the temptation to buy one, but this time it was too much, and I ordered my lovely new lens earlier this month.

Leica SL
Leica SL

APO Lenses, Contrast and Depth of Field

The almost zero aberrations (especially chromatic aberrations) in the new Summicron SL lenses means a big increase in contrast where the image is in focus. As you move away from the point of perfect focus the contrast drops sharply.

This means that the transition between ‘sharp’ and ‘bokeh’ is defined more quickly and results in smoother out-of-focus areas than in conventional lenses. I have a diagram drawn for me by Peter Karbe in my notebook, but here is the graph from the Leica website comparing the APO Summicron-SL 75 with the Summilux-M 75.

The result of this is not just that the 75 APO SL is sharper (it certainly is), but that it has apparently the same death of focus as the 75 Summilux-M. The MTF figures for the 50 APO are even better, and so the effect is even more visible.

Leica SL
Leica SL

We thus have a series of modestly sized Autofocus lenses for the L-mount which perform better than their aspherical competitors and without any depth-of-field disadvantage. Of course, they gather less light, but that isn’t often a problem with modern sensors.

Leica SL
Leica SL

MTF Curves

When Peter Karbe made his presentation at the 50th anniversary LHSA meeting in Wetzlar in October last year he discussed the advantages of making shorter lenses APO Chromatic and when he showed the MTF curves for the 35 APO Summicron. There was a pause, then a huge spontaneous round of applause.

The MTF curves for the 50mm are similarly excellent, and it’s worth noting that they now include values for close focusing which are nearly as good as those at infinity.

To put this in perspective, it’s worth looking at the MTF curves for Leica’s great ‘standard’ lens, the 50mm Summicron M. This classic lens was designed by Walter Mandler and released in the early nineties, it is still on sale today, and much loved for it’s small size and excellent rendering.

This is not meant as any criticism of the older lens, but as an indication of how far Leica have come with their lens design. I should mention that the 50 APO Summicron M shows values much more similar to the SL lens — but still not as good.

Leica CL
Leica CL


It’s all very well talking figures (sorry), and I’m always a little wary of proselytising about the ‘Leica Look’. It would be easier if I could actually define it. I just love the results this lens produces; most of the images in the attached gallery were shot at wide aperture (often at f/2) and there seems to be a real glow about them. This isn’t just evident at base ISO where you might expect it, but right up to ISO 6400 and beyond.

Leica SL
Leica SL


A year ago I was a little worried about the future of the L-mount. Lenses were not coming so fast and, although there were lots of vociferous devotees, the mount system seemed to be running out of steam.

The announcement of full-frame mirrorless cameras from Canon and Nikon during the summer appeared to re-ignite interest, especially as the SL still had some obvious advantages over the new entries (better EVF, two card slots and so on).

However, the L-Mount Alliance announcement at Photokina changed everything. Less than a year later there are two fine cameras and three excellent lenses from Panasonic. And the Sigma lenses are beginning to appear in the wild. (I did a write up on the Lumix S1 and the three lenses here).

I think that these APO-Summicron lenses will end up being the core of many photographers’ L-mount systems (both professional and amateur). I would love to own them all, but I’m very happy to have the 75 and 50 (not because they’re better, but because they suit my photography).

The bokeh is lovely, both in front and behind the point of focus and you can shoot the lens at any aperture with absolute confidence that the results will be fantastic.

The autofocus is fast and quiet and the manual focus, although ‘by wire’ is excellent and precise. On the Panasonic you can choose whether to have ‘accelerate’ or ‘linear’ focusing, and hopefully this will be available on the next SL camera.

It’s back to the superlatives, but as far as I can see, this lens is as near to perfect as one can possibly expect.

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  1. excellent article, thanks ! have spent most of my foto activity shooting colour but learned the art of photography many,many years ago on the wonderful olympus half frame. have just recently returned to shooting in monochrome so was especially interested in your black and white sample images….all I can say is they are stunning with this leica summicron 50mm f2 !!! thanks once again. zen billings in canada

  2. Many thanks
    what is the major difference in Focus and MTF between sl 20 f2 and SL 75f2?
    Bokeh / reaction of out of focus

  3. Character and “Glow” are things typically beeing absent on lenses designed by Mr. Karbe. Just my 5 cents. Owned some of them and sold all of them. Crazy sharp, from a technically point of view pretty much flawless, but also boring.

    • If you want flaws or “characters”, just get vintage lenses. Modern lenses are meant to be perfect. I’m very satisfied with my SL lenses.

  4. Hi Jonathan, you are responsible for me buying a SL and the superlative 24-90 lens which I sold both due to car accident April 2018 which gave me no balance and whiplash so I unloaded heavy stuff and focused on my lovely Panasonic G9 system. Also, there were few f/2 SL glass options at the time. However, my physical health is improving and the Leica summicron glass is on my short list. I purchased the lovely Panasonic 50/1.4 lens so will be not going for this incredible lens but plan to go for Leica f/2 24mm, 28mm and the 90mm which is currently available. I hope you provide reviews of the wide angles as your viewpoint is so competent and artistic.
    Your combination of technical and artistic competence is a breath of fresh air in the on line noise.

  5. “..This means that the transition between ‘sharp’ and ‘bokeh’ is defined more quickly and results in smoother out-of-focus areas than in conventional lenses … The result of this is not just that the 75 APO SL is sharper (it certainly is), but that it has apparently the same de(p)th of focus as the 75 Summilux-M..”

    Mmm. That’s why I swapped my 50mm f1.4 M for the smaller 50mm f2 apo M; the apparent depth-of-field is almost the same, but the resolution and the transition between in-focus and out-of-focus is, as Peter Karbe keeps saying, more noticeable.

    But the 50 apo M is of a small and reasonable size – smaller and a bit lighter than the f1.4 – whereas the 50mm apo L is relatively (..pauses while works up the energy to say..) -H-U-G-E-

    (Of course it’s full of automatic diaphragm and autofocus gubbins, besides the glass.)

    And yet Leica (or Leitz) built their name on -s-m-a-l-l- cameras and lenses you could pop in your pocket. So perhaps the SL and its lenses should be called the Leica “Irony” model.

  6. Nice images and review Jono – and Mike.

    The only concern for me is that weight factor – this lens is only marginally lighter than my Df! When you add that to the SL that’s a fair old chunk of gear you’re carrying. My neck aches just thinking about it, I stopped using the D300s owing to the weight even though I’d slung it on sunpiper camera strap, so it hung upside down and across my body. Good for shooting a wedding, a pain everywhere else.

    • Thanks Dave
      As for the weight – I don’t really carry it around my neck – I carry it in my hand (and swap hands occasionally) – I’ll have a small back over my shoulder with either an M or perhaps the 24-90 in it. (And I am very old and cronky!)
      All the best

    • Thanks, Jono… Actually, I made up the page without looking at your version, so perhaps that’s a good way of creating a little difference. I’ll remember that in future. Excellent photos, as usual, and I am impressed with the results from all three cameras. As I said earlier today in an email, the little CL performs really well and, if you fancy a lightweight rig (even with a 650g lens), it’s worth bearing in mind. Thanks again for allowing us to publish your review.


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