Real-world autofocus experience

We spent some time shooting with a selection of Four Thirds lenses, including the 14-54mm F2.8-3.5 II and 12-60mm F2.8-4, to get a feel for how well the E-M1 is able to really support Four Thirds users. Our experiences were fairly positive, but only when seen from a 'DSLR trying to do live view' perspective, since the situation is comparable (a camera trying to focus a PDAF-optimized lens, without a standalone PDAF sensor).

Focus is usually acceptably fast, though the lenses were prone to slowing down and juddering into focus. This behavior is particularly apparent when switching focus from distant to near objects or when shooting in moderate-to-good lighting levels (inside a well-lit office with large windows). Predictably, both Four Thirds lenses slow down quite a bit in low light. Both struggled focusing at full telephoto, stuttering and occasionally giving up altogether. They're not unusable, but neither are they as good as native lenses here.

Below you'll see how the 12-60mm F2.8-4 Four Thirds lens with adapter compares to the 12-40mm F2.8 Pro Micro Four Thirds lens. The dim office lighting and switch from a very close subject to the chair a few feet behind it provides a significant challenge to both lenses, but the 12-60mm is clearly having more trouble than the 12-40mm. In the telephoto demo below, you'll see (and hear) the stuttering we refer to as the Four Thirds lens acquires focus.

At wide angle the effect isn't as pronounced, though you do see the E-M1 fail to give an AF confirmation in a couple of instances. By contrast, performance is about as fast as you could ask for with the 12-40mm Pro lens.

The 12-60mm didn't do quite as badly outdoors. At wide and telephoto, both Four Thirds lenses we tested displayed some slight stuttering and hesitation in locking focus, but they're slow only in comparison to the extremely fast auto focus performance of the E-M1 with 12-40mm F2.8 lens. For most purposes, they're fully usable in good light.

The way we see it is this: if you're a Four Thirds lens owner and hoping for contemporary DSLR performance, you're going to be disappointed. However, if you want a camera that offers a considerable step up in image quality, that allows you to continue to take great images with your existing lenses and welcomes you into an impressive and growing new system, then you'll be delighted.

Which isn't to say the focus is bad - our first impressions are that the performance is consistent with Canon's EOS 70D, which offers some of the best live view focus of a conventional DSLR. However, for the very best performance, the E-M1 should be used with Micro Four Thirds lenses.

Continuous AF/Tracking

According to Olympus' published specs the E-M1 can track focus on a moving object while shooting at 6.5 fps, with a buffer of 60 frames when shooting RAW. At this speed it also gives a live view feed briefly between frames, which makes it easy to pan the camera to keep the subject in the frame, and overall makes the shooting experience very similar to using an SLR. If you don't need focus tracking it can shoot even faster, at up to 10 fps.

Continuous and tracking AF has been a stumbling block for mirrorless cameras, so far, because contrast-detection AF can't give the camera information about where to focus the next shot. Only Nikon's 1 System cameras, with their on-chip phase detect AF, have bucked this trend up until now. Our initial impression is that the E-M1 does similarly well, making it is a big step forward for Olympus. It does a good job of tracking a target and getting a healthy proportion of shots in focus.

The examples below were shot at a press event hosted by Olympus at Castle Leslie in Ireland. In the first set the horse is trotting briskly through the water towards the camera, and in the second it's galloping up a hill. The lens used was the M.Zuiko Digital ED 60mm 1:2.8 Macro, and all of the images were shot at F2.8. We've shown 100% crops from selected frames beneath the main rollovers, but you can click on any thumbnail to download a full size image and check focus for yourself. In both cases the camera has done an impressive job of maintaining focus on the horse, presumably helped by its on-chip PDAF.

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Here we're showing crops from the best-focused of the frames - frame 9 is visibly out-of-focus at the pixel level, for example. There's a also a slight gotcha in this sequence - despite the camera being set to 6.5fps, it's only actually shot at 4fps (it's quite possible the it was set to 'focus priority' rather than 'release priority' in continuous mode, slowing it down). Even so, it's clear that the E-M1 has successfully held focus on the horse where previous Olympus models would have almost certainly given up.

Touch Focus

The E-M1's touch focus can be used to select a focus point in still and video shooting. With continuous focus enabled, this becomes a useful way to 'pull focus' and switch smoothly between subjects at different distances. The E-M1 does a nice job of this - making a smooth transition between subjects and staying focused where it's directed. In the video below, we change focus from buildings in the background to our subject in the foreground, then to the tree about a meter behind him.

1920 x 1080 60p, H.264 .MOV file, 13 sec, 16.8 MB Click here to download original .MOV file