Best camera 2015: we help you choose the right camera

Compact cameras, D-SLRs, compact system cameras – we explain them all, and where they fit in

Want the portability and convenience of a compact camera but with the ability to attach different types of lenses? Then you should think about an interchangeable-lens compact system – or mirrorless – camera.

If you've decided this is what you want, see our Best mirrorless compact system camera guide. If you're still not quite sure, keep reading.

As the name suggests, the don't use the mirror arrangement found in SLRs, but they do include the same kind of high-quality sensors and processors found in digital SLRs.

The lack of a mirror allows a much slimmer body design, and some mirrorless compact system cameras are barely larger than a regular compact.

Panasonic GM1
Mirrorless compact system cameras are much slimmer than D-SLRs.

Like digital SLRs, most compact system cameras use APS-C size sensors. The big exception is the Micro Four Thirds sensor used by Panasonic and Olympus. This is a little smaller than APS-C, but still much larger than the sensors in most compacts, so the quality level is still much higher.

This slightly smaller format means that Micro Four Thirds cameras and lenses can be amazingly compact. the Panasonic GM1 is no larger than a high-end compact camera, and the Olympus OM-D E-M10 offers the look and feel of an SLR in a far smaller package.

The bigger sensors in compact system cameras mean bigger lenses too, but some makers are now kitting out their cameras with 'power-zooms' – the zoom retracts when the camera is switched off to make the camera/lens combination much more pocketable.

Olympus OM D E M10
Like some other compact system cameras, the OM-D E-M10 has retracting 'power zoom' kit lens.

You only get this with certain kit lenses, though – once you start using telephoto lenses, macro lenses or other types, you'll soon realise they are almost as bulky as SLR lenses, so the size advantage of mirrorless bodies will diminish if you like to carry lots of different lenses.

As with compacts and SLRs, the CSC sector now caters for every type of photographer, from non-technical beginners to professional users. If you're considering a CSC, there are some key considerations to help your buying decision.

The main thing standing in the way of a much broader uptake in the professional market is lens availability. If you're a pro photographer, you will occasionally need specialist lenses that may not be available for this kind of camera – yet.

At the moment, most compact system camera makers cater really well for the beginner/enthusiast market, but are only just getting up to speed with lenses and accessories for pros – though this is changing fast.

Sony A7r
The full-frame Sony A7r is bringing compact system cameras into the professional arena.

Another key factor to take into account with mirrorless compact system cameras is that they don't all have viewfinders. The mirrorless design means that all the viewing is done using LCD displays – there is no optical viewfinder – but some models do come with electronic viewfinders, or 'EVF's. These can be very useful in bright lighting, when a screen on the back of the camera can be quite hard to see.

Fuji X T1 viewfinder
Look out for compact system cameras with viewfinders – it makes a big difference.

Compact system cameras also use technologies from the compact camera and smartphone markets, notably touch-screen control and wireless (Wi-Fi) remote control and picture transfer. These features are creeping into the digital SLR market too, but mirrorless compact system cameras are taking the lead with these new technologies.

They also lead the way in live view autofocus. They can't use the conventional phase-detection autofocus sensors used by SLRs, but the makers are finding ways to introduce hybrid 'on-chip' phase-detection focusing, and advances in regular contrast autofocus, both of which deliver autofocus speeds that match or even exceed those of SLRs.

This is especially important for shooting video, where you need live, real-time autofocus while you're filming. Many professional videographers currently use video-enabled SLRs, but mirrorless compact system cameras like the Panasonic GH4, Fuji X-T1 and Sony A7 are luring users away.

So which do you choose?

That's a lot to think about, so here's a quick summary:

If you want an easy, undemanding snapshot camera to carry around with you, you need a compact camera. This group also includes 'bridge' cameras with the look and feel of an SLR and a huge zoom range, and high-end compacts that give you serious quality and control in a camera you can put in a jacket pocket. See our Best compact camera guide.

If you're serious about photography, however, you should look at a digital SLR instead. They offer interchangeable lenses and more direct manual control, so they're ideal for taking your photography to the next level – and an SLR is a must-have if you intend to take up photography as a living. See our Best D-SLR guide.

But mirrorless compact system cameras now offer a compelling alternative to both compact cameras and digital SLRs. The cheapest are small, inexpensive and easy to use, while the best can match the quality, features and – soon, we hope – the lens range of a digital SLR. See our Best mirrorless compact system camera guide.