Sony FE 100-400mm f/4.5-5.6 GM OSS
Andy Westlake tests an impressive lens that’s perfectly matched to Sony’s high-speed Alpha 9
we test this lens designed for the Sony a9
Acouple of months ago, I got my hands on one of the first samples of the Sony Alpha 9 to arrive in the UK. This full-frame mirrorless wonder can shoot at fully 20 frames per second using a silent, low-distortion electronic shutter, and even more impressively, adjust autofocus and exposure between each frame. The A9 is surely a sign of where camera design will end up in the future, but one thing was missing – the ability to couple it with the kind of native FE-mount long telephoto lens that sports and action shooters are likely to use.
Now the first such lens has arrived, in the shape of the FE 100- 400mm f/4.5-5.6 GM OSS, which Sony also likes to give the decidedly opaque label SEL100400GM. This relatively compact, lightweight optic is a member of Sony’s G Master family, which represents the company’s top-level optical designs. But, at £2,500, it doesn’t come cheap (Canon and Nikon’s equivalents are closer to £2,000). To find out more about it, I put the lens to the test shooting fast jets at the Royal International Air Tattoo at Fairford, Gloucestershire.
Features
The FE 100- 400mm GM is designed as a high- end telezoom, and it has all the features we’d expect from a lens of this type. The optical formula comprises 22 elements in 16 groups, with two extra-low dispersion (ED) glass elements and one super- ED element employed to keep chromatic aberrations to a minimum. Nano AR coating suppresses internal reflections to minimise flare and ghosting, while a fluorine coating on the front element repels grease and water. For close-up shooting, the lens has a minimum focus distance of 0.98m, giving a maximum magnification of 0.35x, which counts as best in class by a whisker.
Sony has built in its Optical Steady Shot image stabilisation, which provides
conventional two-axis stabilisation with APS- C E-mount bodies or the firstgeneration Alpha 7 bodies that lack in-body systems. Mount it on a second- generation Alpha 7-series model, Alpha 9 or Alpha 6500, and the OSS works in concert with the camera’s in-body image stabilisation to provide five axes of correction.
Build and handling
Build quality is every bit as good as we’d hope for the price, and certainly a match for the Canon and Nikon equivalents. Sony has employed a magnesium-alloy barrel construction, with an array of seals to keep dust and moisture at bay, including one around the outside of the bayonet that protects the vulnerable interface with the camera. While I was using it, the lens shrugged off a couple of heavy showers with no ill effects whatsoever.
While the lens is about 1cm longer than Sony’s Alpha-mount equivalent, the 70400mm f/4-5.6 G SSM II, it’s over 100g lighter. Couple this with the much lighter weight of the Alpha 9 compared to top- end fullframe DSLRs, and you have a much more manoeuvrable combination. I was perfectly happy using it handheld throughout an eight-hour flying display.
As usual there are two main controls on the barrel in the shape of zoom and manual-focus rings, along with an array of additional buttons and switches. The zoom ring rotates 90° between the lens’s shortest 100mm position and its maximum extension at 400mm. You can also grasp the lens hood and use it as a push-pull zoom. This is facilitated by a really neat feature – a rotary torque adjustment ring immediately behind the zoom ring. Set this to Smooth and you get quick adjustment ideal for push-pull operation, although there’s some tendency towards zoom creep. Adjusting the torque towards the Tight position eliminates the creep, at the expense of making it a little more difficult to adjust your composition.
At the front of the lens is a non-rotating 77mm filter thread. A deep cylindrical baynet-mount lens hood is supplied, which has an inset sliding door that can be used to adjust polarising filters from underneath the lens, without having to remove the hood or poke your fingers in from the front.
Towards the back of the barrel is a collar that holds the tripod mount foot. It rotates extremely smoothly, but there are no click stops at the 90° marks for the portrait and landscape positions. I particularly like the design of the tripod foot, which detaches from the collar by twisting a lever on its side, then pressing a button on the front. This makes it really easy to remove the lens from a tripod.
Four switches adorn the left side of the barrel, with the top pair for focus and the others for image stabilisation. The AF/MF switch is joined by a smaller focus limiter that prevents the lens from hunting for subjects closer than 3m – useful when you’re shooting distant subjects. Below the Optical Steady Shot on/off switch is a mode selector, with Mode 1 for general use and Mode 2 for panning with moving subjects. Finally, three AF-stop buttons are arrayed around the barrel at 90° intervals between the zoom and focus rings. These can alternatively be set to operate an array of different functions via the camera’s menu, including eye-tracking autofocus and depth- of-field preview.
‘From over 5,000 frames, only a few were out of focus’
Autofocus
With a lens such as this, fast, accurate autofocus is critical. It has to be able to acquire focus extremely quickly, then continuously adjust to track subjects moving towards or away from the camera. To achieve this, Sony has included a complex AF system with one focus group driven by a double linear motor, and a second by a Direct Drive Supersonic Motor (DDSSM). It works superbly.
Autofocus is incredibly quick, supremely accurate, and effectively silent. It would lock on to the subject in a fraction of a second, and track fighter jets making high-speed passes towards or away from the camera. Focus tracking works happily with the Alpha 9’s 20fps full-speed shooting, and during video recording as well. From over 5,000 frames that I shot, only a few were out of focus, usually at the start of a burst. Manual-focus override is available at any time, using the electronically coupled ring at the front of the barrel.
Performance
As you can see from our Image Engineering tests, the lens is very sharp indeed, even at maximum aperture at the long end of the zoom where telephoto zooms are usually at their weakest. In practical terms this allowed me to shoot at f/5.6 to keep shutter speeds high, while keeping the ISO relatively low.
There’s barely any visible chromatic aberration, and just a hint of pincushion distortion towards the long end. The only point of note is that on the full-frame Alpha 9, fairly strong vignetting is visible with wide- open apertures, but this is easy to fix in software.
Image stabilisation is, of course, an important aspect of this lens’s performance, and Sony’s Optical Steadyshot does an exceptional job. With OSS enabled, I was able to get consistently sharp images at shutter speeds as slow as 1/6sec at 100mm, and 1/25sec at 400mm, which represents at least four stops of stabilisation.