Overall Performance

The E-P3 is overall an impressively fast and responsive camera. Autofocus is blisteringly fast, at least with static subjects, and thanks to some intelligent buffering its continuous shooting performance is pretty good too (although its 3fps frame rate is beginning to look a little sub-par against the competition). Meanwhile all other operations - startup, browsing through images in playback, or navigating through the various setting screens and menus - are performed quickly and with no fuss. Fundamentally, unlike some of its predecessors, the E-P3 is a camera that hardly ever feels like it's getting in the way while you're using it, and that's exactly what you want.

Continuous Shooting and Buffering

The E-P3, like previous PENs, has a single continuous shooting mode of nominally 3fps, which by current standards isn't especially fast in this class. Again like previous PENS (and in contrast to current Panasonics) it's somewhat hamstrung for any serious action work by the fact that live view isn't maintained during continuous shooting. Instead you get shown the picture you've just taken, which isn't very helpful when trying to track moving subjects. Live view does however return quickly once you take your finger off the shutter button, and the camera doesn't insist on writing all of the images to card before allowing you to shoot again, so you can mitigate this to some degree by shooting in a series of short bursts. The E-P3 will shoot a series of frames at full speed in an initial burst, then once the buffer is full slow down and shoot at a reduced frame rate. The number of frames you get in the initial burst, and the subsequent slower frame rate, are both highly dependent on file write times (and therefore on card speed and file sizes). This means that you can get noticeably faster performance shooting JPEGs at Fine rather than Super Fine compression, for example, especially when using a relatively slow card (and they're to all intents and purposes visually indistinguishable anyway).

The table below summarises the number of frames that can be shot at full speed before the buffer is full, the reduced frame rate that follows, and the write time for all images to clear the buffer, using two Class 10 SDHC cards across a range of image quality settings. In all cases our measured frame rate for the initial burst was 3.2 fps, slightly faster than advertised. There's a considerable difference between the cards (the SanDisk works out almost twice as fast as the Lexar in these specific tests), so if you do a lot of continuous shooting it's worth getting hold of the fastest card you can.

File format
SanDisk Extreme Class 10*
Lexar Professional Class 10**
Full speed buffer
Reduced frame rate
Buffer clear time
Full speed buffer
Reduced frame rate
Buffer clear time
8 frames
0.7 fps
13 sec
8 frames
0.35 fps
22.5 sec
9 frames
0.8 fps
10.5 sec
8 frames
0.4 fps
17.5 sec
11 frames
1.3 fps
7 sec
9 frames
0.7 fps
12.5 sec
13 frames
1.6 fps
5.5 sec
9 frames
0.8 fps
10 sec
17 frames
2.1 fps
4.5 sec
11 frames
1.2 fps
8.5 sec

* SanDisk Extreme SDHC Class 10 4GB 30MB/s
** Lexar Professional SDHC Class 10 8GB 133x

The E-P3 is also compatible with the latest high-speed UHS-I SDHC cards, and in principle these should give even better performance. However in side-by-side testing using a SanDisk Extreme Pro 8GB 45MB/s Class 1 UHS-I card, we found it to offer only a marginal advantage over the 'standard' SanDisk Extreme Class 10, despite being nominally 50% faster.

Autofocus speed / accuracy

Olympus has made great claims about the E-P3's autofocus speed, and it is indeed astonishingly fast when paired with suitable lenses (including the 14-42mm F3.5-5.6 II MSC kit lens), for static subjects at least. Exactly how fast it is, and how it ranks relative other cameras, is almost irrelevant (although for the record, it's at least a fast as any other interchangeable lens camera with kit lens). The point is that unlike the E-P1/2 with the original 14-42mm kit lens, it's fast enough for almost any use. And, like other cameras which employ contrast-detection autofocus using the main imaging sensor, it's essentially immune from the front- and back-focus problems which can affect DSLRs.

The E-P3's autofocus illuminator addresses one of the other big criticisms of previous PENs, which struggled to focus in low light. It's not a panacea - as usual it won't cover off-center subjects, its effective range is limited, and its proximity to the lens means it can be blocked by those with larger barrels - but it's a big improvement, and makes the camera much more usable in dimly-lit conditions.

Once your subject starts moving, though, things are a little less clear-cut. Contrast-detect AF systems have historically been less capable at tracking moving subjects than the phase-detection systems used in SLRs, so the E-P3 has its work cut out to match this more-established technology. In continuous AF mode the camera's continuous frame rate drops dramatically while the camera checks focus between shots: even with a static subject, it'll manage 1.6 fps at best. And the lack of live view means you can't follow your subject between frames in continuous drive mode, so there's no way to ensure it stays covered by your selected AF point.

To combat this problem, the E-P3 also has a subject tracking mode (C-AF+TR) inherited from the E-PL2. Once you've designated a subject by focusing on it initially, then the camera will attempt to track it around the frame and keep it in focus, just as long as you keep the shutter half-pressed. But again, this has problems once you start shooting in continuous drive mode; naturally it only works if your subject stays within the frame (and there's no way of knowing this), and as soon as you release the shutter the camera stops tracking and resets the AF point. It's also easily confused by objects within the frame that are even approximately the same colour as your specified subject, and will happily switch its attention to these instead.

All-in-all, while Olympus is certainly making some progress in this area, the E-P3 still isn't the most practical camera for shooting moving subjects in the real world, even compared to other mirrorless cameras. For example Panasonic's implementation of continuous drive mode mode maintains live view between shots, with AF tracking that stays locked onto your subject until you reset it. Pretty well any SLR will do better too.

Battery life

The E-P3 uses the same BLS-5 battery as recent PENs, and it's rated to 330 shots by the CIPA standard. This is marginally higher than the E-P1 and E-P2, presumably reflecting decreased power demands from the OLED screen. Given how much more usable the screen is than the old 230k dot display, this can only count as a bonus. Because the E-P3 is also compatible with the older BLS-1 battery, it's also pretty straightforward to get hold of a spare or two, which we'd recommend if you're planning on doing any extended shooting.