Compact system cameras (CSCs) sit between the advanced compacts described earlier and the more professional DSLR cameras. Their key advantages are that they use the same kinds of sensors and processors found in DSLRs, and that they are compatible with a range of high quality, newly developed lenses, designed for specific tasks.
So, unlike with compact cameras, where you have a fixed, all-purpose optic, you can alternate between a standard kit lens for everyday shooting, a macro lens for detailed close-up shots, and a telephoto lens for nature and sports photography, among other options.
Manufacturers are targeting several different users for this new breed of camera, from first-time users demanding an inexpensive way of attaining high-quality results, right through to enthusiasts and professionals who need a smaller alternative to their DSLR body and lenses. This means there's quite a bit of choice.
Best compact system camera
Suitability for all users
The CSC format has only been in existence since September 2008 when Panasonic announced the G1, but it has been widely deemed a great success.
For the novice user, such cameras provide the ease of use of compacts and fun-orientated functionality such as special filters and effects, while for the more advanced photographer they add manual control, raw shooting and image quality of a standard equal to similarly-priced DSLRs.
With no moving mirrors they are also more discreet than DSLRs, and what operational sounds there are can often be quietened or almost completely silenced if required.
It doesn't stop there though. Their LCD screens typically match the quality of those found on professional DSLRs, with many offering touchscreen control. The electronic viewfinders on certain models are far more detailed than those on bridge cameras, which is particularly useful for judging focus.
The CSC's mirrorless construction also allows for particularly fast burst speeds, while HD video recording is now commonplace.
Furthermore, a vast assortment of adaptors enable older optics from entirely different and defunct mounts to be used with little hassle, making them particularly appealing to seasoned photographers with a collection of legacy lenses.
Which camera is right for your needs will depend largely on whether you'd prefer a DSLR-like body or something more compact, as well as your preference with regards to operation.
Many newer CSCs make use of innovative touchscreen operation rather than physical controls and buttons, and this is likely to polarise opinion. In poor lighting conditions it can help to have virtual buttons located on a screen rather than physical buttons whose purpose may not be clearly seen.
Some touchscreen models enable you to focus and capture images simply by pressing the screen.
On the other hand, many photographers are used to using buttons and dials, rather than poking at and swiping through menu systems.
So what are the downsides of a compact system camera (CSC)?
With the format still in its infancy, the sector is still in the midst of being fully established, and that applies to its lenses and accessories as much as it does to its cameras. That said, the Micro Four Thirds system employed by Panasonic and Olympus has a very healthy array of lenses and accessories, with more optics being produced by third party manufacturers such as Sigma.
Regardless of what camera you go for, you should ask yourself: does the manufacturer have - or is it planning to have - a more advanced model to which I could upgrade? Are the lenses and any accessories I want available and affordable?
Portability and speed
You should also bear in mind that while CSCs may be more portable than DSLRs, you generally can't slip them into your pocket with a lens attached as you can with entry-level and mid-range compact cameras. The exception to this is when using certain CSC bodies with pancake lenses, the combination of which is similar in size to that of a compact model.
The lenses of advanced compacts often retract into their bodies, or generally only add a few millimetres to the overall profile.
As compact system cameras in part owe their small size and weight to the lack of a mirror that reflects light into a DSLR's viewfinder, they also lack an optical viewfinder. Some offer an electronic alternative, but not everyone likes them, even though their quality has improved recently.
While some cameras don't have a viewfinder, others have a port that enables an optional viewfinder to be attached. The electronic viewfinder (EVF) shows the image as it will be captured, taking into account the focal length of the lens as well as exposure and white balance settings.
In some cases it's possible to mount an external optical viewfinder on the hotshoe, however, these are fixed to one focal length, which isn't particularly helpful when using a zoom lens.
Another consequence of CSC's construction is that they don't offer the fast phase-detection focusing systems which DSLR photographers take for granted. The speed of the contrast-detection and hybrid (contrast and phase detection combined) systems used in their place is constantly improving, and in some recent models it's impressively prompt. However, in terms of flexibility, the DSLR still has the overall advantage.