Panasonic Lumix S 40mm F2 (S-S40) lens review

What is it?

The Panasonic Lumix S 40mm F2 is a super-lightweight and compact, budget-friendly standard lens designed for the full-frame Panasonic Lumix S mirrorless camera line. As an L-mount lens, though, it will also fit Leica SL cameras and some Sigma cameras. Falling between the typical 50mm standard and the moderately wide 35mm focal lengths, the 40mm is sought after by those in the know for its indeterminate look. And that applies to photographers as much as filmmakers. Indeed, film-era lenses of this focal length, especially the pancake or four-element Tessar-type, go for relatively high prices today compared with their new prices. While not exactly in the pancake category, like its sibling 26mm fixed focus lens, it’s still very small – it’s some 41mm long – compared with today’s more typical standard lenses. It’s also lightweight, at just 144 g (5.1 oz).

What’s interesting about this new lens, though, besides the focal length, is that Panasonic has brought it right up-to-date. 

The optical design has seven elements in six groups, which include three (?) Glass Moulded (GMo) Aspherical elements and fluorine coating on the front element to aid cleaning. When looking at the lens in cross-section, we can see a Tessar-like design in the first three groups, followed by three additional elements/groups located behind, which is promising. I say that because the Contax Zeiss 45mm F2.8 Tessar has both field curvature and focus shift, the latter typically caused by spherical aberration. So the addition of the aspherical lenses should reduce both the cause and the effect.

MTF Results

Looking at the MTF graph for the lens, which is assumed to be wide-open at F2, we can see it has high central performance extending to the 10mm mark, roughly two-thirds of the central image field, with a gentle falling-off in sharpness to the edges and corners of the frame. Some astigmatic/coma behaviour can be expected with large structure contrast (10 lines/mm), but not so much at the high-resolution 30 lines/mm mark.

Panasonic has not only updated the optical design. Externally, there’s a large ribbed focusing collar that can be customised to act as a control ring and adjust a raft of features. When set to AF, the collar is largely redundant, so customising it makes a lot of sense. While not unique to Panasonic, the breadth of choice probably is. During the review period, I set it up to adjust ISO, but you can choose from a long, long list.

There’s also a small customisable button that can also do the same, depending on the camera in use, anyway. I was sent the Panasonic Lumix S1R II, which offers a wide range of features. I set the button up to cycle through the different AF modes. Furthermore, pressing and holding the button for a few seconds brings up the custom menu so you can change it on the fly. There are some esoteric choices on the S1R II: I can’t recall reviewing a more customisable camera.

Even though this is an accessibly priced lens, it has a fluorine coating on the front element to help when cleaning, and it’s also sealed against moisture and dust. 

How does it perform

In terms of focusing, the 40mm is pretty fast, perhaps not instantaneous as such, but I don’t expect anyone to be disappointed. It’s also very quiet and smooth during refocus. During my review, I deliberately used autofocus instead of my preferred manual focus to check for focusing noise, but I couldn’t hear any in the video samples I made.

Aperture-dependent focus shift is an issue with the highly-regarded Contax Zeiss Tessar, so I was curious to see if the Lumix S40mm F2 suffered from the same fate.

Most of the sample photographs were made using the Fine Focus option of the Lumix S1R II, as accurate focus is required to assess lens performance (obviously). Photographing certain subjects, low-contrast mainly, was an issue at times with the lens focusing behind high-contrast elements. Take the photographs of the Alliums, for example: several of the dozen or more I made show the plane of focus behind the intended point. Initially, I was concerned that it might be a result of a focus shift (even when made wide open, depending on the AF system). However, I’m convinced, after more testing, that this was due to user error. Selecting a different AF mode at the time would have produced an acceptably in-focus result.

As for sharpness and contrast, the lens is a very good performer wide open, certainly centrally. There’s the slightest hint of SA, some slight LaCA/fringing and out-of-focus backgrounds with hard-edged subjects can look a little busy, or “nervous” at times, but it’s not objectionable. Indeed, I think the results are impressive. Vignetting and distortion are low, too, and that’s with profile correction turned off. Applying the profiles in Lightroom Classic, for example, does a fair job, but the LaCA/fringing can be persistent; you can get better results by switching to manual correction. Stopping down, sharpness increases slightly centrally, but most of the improvement here is at the edges of the frame, though it never quite matches the centre.

Overall, the lens is a great performer with an attractive drawing style. 

The lens is available in black or chrome, and while I’ve never been a fan of the black body and chrome lens aesthetic (chrome or safari coloured camera, chrome lens I get), I am coming to terms with it somewhat.

Conclusion

Small, light and with a “fast” aperture, the Lumix S 40mm F2 (S-S40) is a highly appealing lens for the L-mount, and especially for the smaller bodies like the Lumix S1R II. It’s very sharp centrally and has a distinctive and not unattractive drawing style: the softer edges, wide open, help highlight subjects placed centrally. It’s no slouch either when it comes to focus speed, and it’s both quiet and smooth for filming. At £349 inc VAT, and with weather sealing, a customisable focus ring and a function button, it’s an attractive lens that goes against the trend of the high-priced optics since the mirrorless cameras arrived on the scene. 

Technical Data

Check prices and preorder the Panasonic Lumix S 40mm F2 (S-S40) at the following retailers: