A review of the Sigma 16mm f/1.4 DC DN lens for m4/3

I’ve said many times on this blog that my favourite focal length is 35mm (35mm equivalent) which give a diagonal angle of view of 63.4º To me it is a relaxing normal view, I find 50mm a bit too tight and 28mm a bit too “loose”. So when I migrated from so-called full frame to micro four thirds in 2010 one of the first lenses I bought was the Olympus m.Zuiko 17mm f2.8 pancake lens. Actually at the time there were only three lenses in the system the 17mm, a 14-42mm kit lens and the 40-150 telephoto kit zoom and I ended up getting them all.

The 17mm was equivalent to 34mm in in full frame terms and has a diagonal angle of view of 65º, so close enough as not to make any real difference. It wasn’t a well received lens despite being what initial advocates of the micro four thirds said they wanted – pancake lenses. It’s slow maximum aperture of f2.8, slow and noisey auto focus combined with less than stellar optical performance put many people off and they went for the much more expensive Panasonic 20mm f1.7 which had the virtues of being optically better, and having a faster maximum aperture. It still wasn’t great in the AF department though. But hey these were the early days of mirrorless technology and AF systems were not very quick and accurate then. But anyways I got the Olympus in a kit with my Olympus EP2 and I actually loved it. I could slip it mounted to the EP2 in my pocket which made it a great stealth camera combination and I used it to shoot my TransPerth-Transhumance project. I still use the lens today, mainly on my EP5. The area where I felt it was absolutely hopeless was video. The AF was too slow, too noisy (think angry wasp stuck in a jar) and I wanted a bit more subject isolation than the f2.8 aperture could give.

So fast forward a few years and I’m shooting more and more video and I decide to get myself a better 17mm lens. In the intervening years Olympus had produced the very favourably received 17mm f1.8 and the eye-wateringly expensive f1.2 version. Panasonic had also come to the party with their Panasonic Leica Summilux 15mm f/1.7 lens. In fact I went to my local (if you can call 110Km away local) camera dealer to buy this lens and it was always out of stock which made me want it even more. But in the end I went for an outlier in the form of the Sigma 16mm f/1.4 DC DN lens. The reasons being that f1.4 is faster than f1.9, it was cheaper than the f1.2 and the difference between f1.2 and f1.4 is slight, and my dealer had it in stock. So what makes it and outlier? Well to put it bluntly it’s bloody huge. It has a 67mm ⌀ filter thread which compares to 37mm for the Olympus 17mm f2.8. It is bigger than the Olympus 12-40mm f2.8 and the Panasonic Leica 8-18mm f2.8-4 while being only a little shorter than the Olympus 75-300mm f4.8-6.7. The 16mm focal length equates to 32mm on full frame with a diagonal angle of view 68.1º so is a bit wider, but when used with the Panasonic G85 for 4K video this isn’t much of a problem as the camera crops in slightly. So how come this lens is so lardy I hear you all ask. Well this lens wasn’t designed for micro four thirds, it was initially designed for the Sony 6000 series cameras with an APS sized sensor where it equates to being a 24mm in full frame terms. To get a wide angle lens that’s fast and a good optical performance means lots of glass and glass is heavy, and this lens is large and heavy for APS format cameras. To get some additional return on their investment Sigma decided to offer the lens in micro four thirds mount hence it seeming a funny focal length and being bigger than necessary.

Vital Statistics

In the hand the Sigma 16mm feels very dense and substantial. The lens body is made out of what Sigma calls a Thermally Stable Composite (TSC) which is substantially stronger than conventional polycarbonates while having similar thermal expansion properties to aluminium. The lens mount is made of chromium plated brass which should ensure a long life. The Sigma 16mm is advertised as being dust and splash proof but on closer reading of Sigma’s spec sheet there is only one seal and that is at the lens mount. The lens comes with a bayonet mount petal lens hood which has a ribbed grip to make attaching and detaching easier. While it is good that the lens comes with a hood it’s not the best implementation and feels quite insubstantial and can be fiddly to attach as it can foul and not lock home. There is a ribbed rubber focus ring of the fly by wire type – it feels smooth and easy to use. There are no other controls or switches which means if you want to switch between AF and manual focus you will have to use the camera controls for that.

The Sigma 16mm has an optical construction of 16 elements in 13 groups with 3 FLD (“F” Low Dispersion) glass elements, which offers performance equivalent to fluorite which exhibits less chromatic aberration than those utilising a traditional flint glass. There are 2 SLD (Special Low Dispersion) glass elements which also help to minimise chromatic aberration and 2 ASPH moulded glass aspherical elements which work to reduce optical aberrations. According to Sigma’s website the ASPH elements are polished with a tolerance of under 10 nanometers or 0.000001 millimetres which according to Sigma reduces onion ring bokeh.

Performance

In terms of autofocus the stepping motor is fast and accurate and very smooth when shooting video. I tested the lens on the OMD EM1 mk ii which has on sensor phase detect AF and on the Panasonic G85 which uses DFD technology – a variant of contrast detect auto focus that requires the lens to provide a profile to the camera to ensure fast and accurate AF. The Sigma does not have such a profile as these are limited at present to only Panasonic’s own lenses. Despite that there were no problems and I could detect no discernible difference between the Olympus and the Panasonic. The only downside in the AF department is that I can’t use the Pro Capture Low setting which gives up to 18 fps with auto exposure and AF tracking. This is no fault of Sigma’s as the option is only available with Olympus lenses.

Optically – well straight from the get go the Sigma is impressively sharp wide open corner to corner. The performance improves slightly (and it is only visible on my 4K screen at 300%) as you stop down. Diffraction sets in at f16 and this does soften the image. In terms of chromatic aberration, well wide open in high contrast situations it is apparent albeit slight and it is easy to correct in post. The lens is reasonably resistant to flare – but if you have a specular light source in the frame you will experience some veiled flare and ghosting. If you turn off the built in lens profile you can observe a slight barrel distortion, but switch on the profile and it is not visible. The bokeh balls this lens produces are more or less round when shooting wide open even at the edges of the frame and the transitions are nice and smooth. There is some onion ring bokeh which is the result of using moulded aspherical lens.Vignetting is not a problem and is very slight in the region of 1/2 stop.

Verdict

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Being designed to have an image circle much larger than micro four thirds requires means that you are using the best performing part of the lens and this really shows. Just for giggles I compared the Sigma with my old Olympus. The Olympus is noticeably soft in the corners at all apertures and just average in the centre. It suffers badly from chromatic aberration. Vignetting is very apparent, in excess of 1 stop in the corners with the lens profile switched on and getting on for 2 stops when switched off. Physically, optically and figuratively the Sigma stands head and shoulders above the little Olympus. The only area where the Olympus wins out is its small size and that is why I’ll continue to use it when I want something small and compact. For every other occasion I’m reaching for the Sigma. The knock on effect is that I’m seriously wondering about replacing my Olympus 45mm f1.8 with the Sigma 56mm f1.4.