This is the second part of my first impressions of the new Olympus m.Zuiko 40-150mm f2.8 Pro lens. The first part is here and covers my thoughts on the lens’s usability, design and image quality. However, this lens (along with its MC-14 1.4x teleconverter and the forthcoming 300mm f4 Pro telephoto) is going to be of considerable interest to wildlife photographers, given its promise of high optical quality and high speed (optically and mechanically) combined with compact size. And it’s here that the performance of the lens+camera system for focus tracking becomes of more than academic interest, so here then are my first ad hoc results from trying the focus tracking with the lens and the camera it’s most likely to be partnered with, the Olympus OM-D E-M1, created with the enthusiastic assistance of two of the faster-moving members of our household.

And yes, these shots are more indicative of the limitations of the lens/camera combination than its potential, shot as they were in a snow storm on a late December day, at a latitude North of Moscow, but I thought I’d gained enough information from the exercise to be worth sharing.

All shots here are from RAW originals, with just setting of levels & contrast, mild sharpening and colour balance in each case. Camera setting were: C-AF+Tracking, IS off; shutter priority; auto iso (limited to 1600 iso); Low continuous shooting (6.5fps). The last is because, at its maximum 10fps setting, the E-M1 only focusses for the first frame. Camera and lens firmware was 2.2 and 1.0 respectively for these tests.

I’ve already established that even the old 50-200mm has no problem tracking a galloping horse, So my first question is whether the new upstart is able to cope with the much, much sterner test of hurtling cats in a Scottish December snow storm?

The answer, in short, is “not quite”. And there I think the prime limitation is the E-M1’s tracking system – the lens itself focussed near-instantly when the camera could get a lock – and I found that if you got a good lock before the subject really got going, the tracking would at least make an effort at keeping up: acquisition of a rapidly accelerating subject was however – and in this test at least – not good but tracking of an object moving at roughly constant speed was rather better.

Now to justify that assertion with some detail: The first sequence of three (shown from a larger set) of Phaedra strolling towards the camera show that the camera/lens combination has no trouble whatsoever tracking her – all shots in the set were perfectly sharp. By the third image displayed here (taken immediately after the preceding one) she had however suddenly fired herself sideways and bounced off a tree. Looking through the viewfinder, the tracking circle did try to stay with her, but the sudden acceleration was too much for it to quite cope with, the focus being quite a long way out.

No problem at a stroll…

Still no problem…

Gone…

For the next set, of which five are shown below in sequence, I’d been expecting a fast launch (having spotted her brother sneaking up on her) so had already locked the tracking point onto her – so the first frame is entirely sharp. In frame two, she’s blasted off ahead of her brother and the focus point is already lagging her acceleration, with the focus plane somewhere around her rear end. As she continues to accelerate in frame 3, the lag gets worse, to roughly 50cm behind her by now. By frame 4, as her initial acceleration tails off, the camera has caught up slightly – parts of her tail are now nearly in focus (allowing for the motion blur from use of a rather low 1/500s shutter speed). In the final frame, she’s moving at more of a constant high speed and the tracking has caught up a little further, with the focus point appearing somewhere around her whiskers. She’s also tracking across the frame more than moving down the lens axis. Again though, overall sharpness is compromised by low shutter speed – more experiments are definitely needed once we have brighter weather.

First frame – here, the focus tracking has locked on to Phaedra as she walks

As her brother piles in, she accelerates – note that the focus point is already lagging – the focus plane is somewhere around her rear end.

The focus point is still lagging her, now by about 50cm.

Here, it’s caught up slightly – parts of her tail are in focus (allowing for a little motion blur).

By now, it does seem to have caught up – the whiskers are sharper (albeit with a lot of blur from the relatively slow 1/500s shutter speed).

For the last shot here I locked the tracking circle on to Moriarty before he walked behind the foreground reeds: here the camera did an admirable job of keeping tracking focus on him, despite the interference of the reeds.

It’s also interesting that the camera definitely has less trouble acquiring and tracking the multi-coloured Phaedra than her mostly blue brother.

My initial conclusion is that this new lens is fast-focussing and accurate but that extreme conditions of this particular test show up one of the remaining limitations of hybrid-focussing mirrorless systems compared with the best of the semi-pro level DSLRs. I will update this review as soon as I’ve found some bright conditions in which to try again. My entirely unsurprising conclusions are that:

• Tracking has less trouble when the subject is at constant speed
• It performs at its worst when the subject is accelerating fast towards or away from the camera
• It’s at its best when the subject is tracking across the camera’s field
• Rapid acceleration outpaces the camera’s ability to keep up.

The lens itself doesn’t seem to be the limiting factor here: subjectively at least, I felt that it was performing better in tracking than the much simpler M.Zuiko 75mm f1.8.