The Olympus OM-D E-M5 Mark II may at first glance look similar to its predecessor, but it's a very different camera underneath. Andy Westlake examines it in fine detail in our Olympus OM-D E-M5 Mark II review
40MP composite mode
The Mark II’s headline trick is undoubtedly its 40-million-pixel composite ‘High Res Shot’ mode. This works by taking 8 images, using the camera’s in-body stabilisation system to move the sensor fractionally between them on order to sample the scene in higher detail. The camera has to be fixed solidly to a tripod for this to work, and because it’s a multiple-exposure process that takes at least a second to complete, anything that moves will show ghosting artefacts.
The mode first has to be turned on in the camera’s menu; this allows you to define a delay before the picture is taken (to allow any vibrations to die away), and even specify a wait time between exposures to allow flash units to recharge, if you’re shooting in the studio. Slightly strangely High Res Shot is then accessed as a drive mode, rather than as a resolution setting where you might expect to find it. You can decide whether or not to record raw files independently of your usual choice in 16MP mode; by default, this option is turned off.
The 8-shot composite raw file is vast – 100MB or more – and recorded with an ‘ORF’ extension, but the camera also writes a conventional 16MP raw of the first exposure with an ‘ORI’ extension. This gives a safety net in case something goes wrong, for example you inadvertently shoot in High Res mode hand-held. Composite raw files can be re-converted in-camera to 40MP JPEGs, with the usual options to tweak exposure, white balance etc. Currently you don’t get the choice to make a 16MP file from the first exposure, but if you rename the ORI file to an ORF using a computer and re-insert the memory card, the camera will recognise it as usual and let you make a 16MP JPEG.
There are a number of limitations on exposure settings. Olympus won’t allow you to set an aperture smaller than f/8, because diffraction blurring at smaller settings will negate the mode’s usefulness, and the longest available shutter speed is 8 seconds to avoid the build-up of thermal noise. The maximum sensitivity is limited to ISO 1600, but it’s worth noting that because this is a multi-shot process that effectively averages noise, the images remain impressively clean.
It’s also important to use a good lens; Olympus’s ‘Pro’ series zooms and fast primes should be able to resolve sufficiently across the frame to deliver the additional detail, but cheaper lenses will struggle with resolving enough detail towards the corners. Ironically this includes both the 12-50mm and 14-140mm zooms that will be sold in kits with the Mark II.
However, when it does work, the high-resolution composite images are impressive. Visibly more detail is recorded compared to 16MP mode, and while it’s perhaps not as much as you’ll get from a 36MP full frame sensor, the difference is very small. Colour moiré is effectively eliminated, too, and noise is very low, even at higher ISO settings. Even so the High Res mode is only suitable for static subjects, and to be honest, nowhere near as practical as simply using a camera with a high-resolution sensor.
But what about when it goes wrong?
When the 40MP mode goes wrong, it tends to do so quite spectacularly. In the example below, I tried unsuccessfully to shoot using a railing as a support. But the camera moved fractionally between shots, and various objects moved in front of the camera too, resulting in a salutary lesson in how not to use a multi-shot mode.
The take-home message here is that you can’t expect to be able to get way with a lot of the camera support tricks you might use for normal shooting if you’re not carrying a tripod with you; instead you absolutely have to use a rock-steady support. Of course, with the E-M5 Mark II’s compact size and small lenses, you can get away with using a relatively lightweight tripod compared to what you’d need for an SLR.
Obviously you also need to take care to avoid having moving subjects in your photos. If you’re taking photographs with moving water, then it probably makes sense to use a strong neutral density filter to blur it, which should give better results than overlaying eight ‘freeze frames’. There’s probably also scope for using the 16MP .ORI file to help patch out any moving subjects, albeit at reduced resolution.