(Pocket-lint) - You're looking to buy a mirrorless camera - sometimes called a compact system camera (CSC) - but don't know what to go for? That's not necessarily a surprise, as mirrorless cameras are more diverse and popular than ever before, with more brands, lens mounts and systems mixing up the offerings.

In this best-of feature, we round up the best mirrorless system cameras of to suit all tastes and abilities. Whether that's based on a budget for a first-time buy, or a larger chunk of cash for a pro-spec full-frame mirrorless model, here's the best DSLR alternatives to consider.

Lens mount

First thing's first: cameras don't work in a one-size-fits-all kind of way. Brands like to keep their own heritage and, as such, manufacturers tend to have individual lens mounts. The exceptions are: Micro Four Thirds, supported by Panasonic Lumix G, both Olympus Pen and Olympus OM-D models; and the Leica L mount, which will offer S lenses from Panasonic and lenses from Sigma.

Elsewhere there are a whole host of considerations, each tied to their respective manufacturers: it's EOS EF-R for Canon's full-frame models and EOS EF-M for its APS-C models; it's E-mount for Sony Alpha (formerly NEX) and A-mount for its full-frame (SLT) cameras; and XF-mount for Fujifilm.

Others are already past their sell-by date: Pentax gave up on the Q-mount for Pentax Q in 2017; NX-mount for Samsung NX (and specifically the smaller NX-M mount for the NX Mini) are both now defunct; and the 1-mount for the Nikon 1-series was also binned in 2017.

Focal length equivalent

Each lens will have a "mm" marking on it, such as 12-24mm, to convey the angle of view it will deliver. The lower the number the wider the angle of view, so more will "fit in" to a given scene.

It's a bit more complex than that, however, as different camera systems have different sensor sizes that give different focal length equivalents, but stick to that rough rule above and you'll have an approximate understanding on what you're getting.

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What the Panasonic Lumix GX800 really gets right is its price proposition. There's a lot of features on offer for its sub-£300 price point, which will see camera keenos flocking to check out this accomplished little mirrorless system.

Downsides are the lack of any viewfinder option (but then just look at the G80/G85 instead, below), some plasticky build elements, limited battery life, that 12-32mm collapsible lens not being the best, and the odd choice of a microSD card (most cameras use full-size SD, but not here).

All things considered, however, those above nit-picks are far from major problems. Especially when decent image quality, an autofocus system that'll better almost anything else at this price, a raft of compatible Micro Four Thirds lens options, 4K capture and accessible touchscreen controls use are all par for the course.

Read our full review: Panasonic Lumix GX800

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Panasonic has boat loads of great G-series cameras. The one that offers the most bang for your buck is the G80. It's like a mini DSLR in many senses, combining a built-in viewfinder with a vari-angle touchscreen LCD to the rear.

With a lot of the technology taken from the top-end G-series line, the G80 walks the line between pro and budget. There's 4K video capture, decent image quality and all the control that you could possibly want. One of our favourite features is Pinpoint autofocus.

If you're looking for a one-stop-shop then few can offer as much as the G80 for the price. If you do have a bit of extra cash and prefer a more compact-style camera then the Sony A6500 is also one credible camera.

Read our full review: Panasonic Lumix G80 review

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Retro done right, that was our sentiment about the X-T20, the cut-price little brother to the X-T3 (further below). Its combination of retro design, quality construction, top notch image quality and decent general performance make it a great all-rounder.

The X-T20's biggest issue is nothing to do with its own performance: it's the presence of the Panasonic Lumix G80 (above), depending on which one you can find for less cash (it's increasingly close).

But while the Panasonic is like the brains of the mirrorless camera world - it's hugely capable, with 4K modes, Pinpoint autofocus and weather-sealing - the Fuji X-T20 is the heartfelt, retro-styled champ. And sometimes it's better to listen to your heart than your head, right?

Read our full review: Fujifilm XT-20 review

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Smaller than the Panasonic offering, yet still with a built-in viewfinder, the A6500 is a highly accomplished little camera.

Indeed, you'll struggle to find a mirrorless cameras with quicker autofocus. The A6500 is up there with the best-in-class in this regard, while its processor is hugely capable of backing up its 11fps burst mode figures. Image quality is great, too, while its 4K video capture will appeal to a whole other audience.

The biggest drawback of the Sony system is its over four-figure asking price. It's really pricey, which is why the Panasonic G80 (above) may appeal more, but for the right user the Sony is certainly worth it. Oh, but its battery life isn't great , so you'll want to carry a spare.

Read our full review: Sony A6500 review

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If you're looking for a DSLR alternative with some added mirrorless benefits then the G9 ticks all the boxes. It's a very impressive bit of kit indeed.

The G9 offers oodles of appeal by cutting out the typical irks that many mirrorless cameras can present: it's got a huge viewfinder with near-instant startup; a super-fast 20 frames per second (fps) continuous autofocus mode at full resolution; it adds a light-up status LCD screen (which you'll find nowhere else except on a mirrorless Leica); and offers improved battery longevity with up to 920 shots per charge.

Having used the Lumix G9 with a variety of lenses for two weeks - in both South Africa on safari and Vietnam while travelling - we've come to think that it's perhaps the finest mirrorless cameras that money can buy. Indeed, it's so good that we'd lean away from the Fujifilm X-T2 (see below) in its favour.

Read our full review: Panasonic Lumix G9 review

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If there's been one inherent weakness for many mirrorless cameras it's their ability to cope with moving subjects. Fuji has tackled this head-on with the X-T3, which is among the best mirrorless cameras for capturing moving subjects.

Beyond just being good at shooting fast action, the X-T3 is an exceptional all-round camera too. It's well built, looks great, the image quality is that high-quality Fuji standard, and there's all the control and decent lens back-up that you could want. We think it even trumps the X-H1 in many regards (and the Panasonic G9, above, is better than that Fuji offering anyway).

Read our full preview: Fuji X-T3 initial review

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If it's speed you want, it's speed you'll get, with this Olympus capable of capturing up to 18 frames per second.

Also principal to its success is the built-in image stabilisation - which is perhaps the best sensor-based system we've ever used - and its super-quick reactions across the board, from start-up, to autofocus, burst speed, capture and playback.

Ultimately, the Olympus OM-D E-M1 Mark II is among the best Micro Four Thirds cameras for advanced photographers shooting moving subjects. That said, the Panasonic Lumix G9 (above) offers an even more compelling 20fps burst alongside a better viewfinder, which will ultimately be more favourable (and it's cheaper than the Olympus to boot!)

Read our full review: Olympus OM-D E-M1 Mark II review

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The X-Pro2 is a camera for the modern professional. Or the nostalgic shooter, given its rangefinder-like stylings.

Sure, it's a quirky camera, but that's what we love about the X-Pro. It stands out from the crowd with its complex "advanced hybrid multi viewfinder" (that's what Fujifilm likes to call it): think rangefinder-like use thanks to a corner-positioned digital rangefinder overlay screen (as found in the X100T) which can show a 2.5x or 6.0x magnification of the active focus point for precision manual focus, ensuring correct focus for close-up shooting.

We'd still like to see a vari-angle touchscreen rather than fixed panel only, but given that the X-Pro2 seems to be looking inwards to its existing pro user base rather than outwards to newcomers, we suspect the target audience will remain happy without.

Read our full review: Fujifilm X-Pro2 review

Video or movie capture has been going from strength to strength in mirrorless cameras, with many now very capable. Our current favourite is the Panasonic, but die-hard videographers may call on Sony's A7S II as the very best model going (something only the Panasonic GH5S can really throw into contention).

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The camera world has been moving at a fairly slow pace over the last few of years, with only small gains to be made. If you were to compare the GH5's image quality to the earlier GH4, for example, then the gains aren't that significant.

But when it comes to video the GH5 offers out-of-this-world top quality. There's 4K capture with 10-bit 4:2:2 output (at 30fps; 60fps is 8-bit 4:2:0) and a host of pro spec features that put it head and shoulders above anything else you can buy at this price point (well, except the company's own GH5S, below)

Sure, it might be pipped in stills quality by the Fujifilm X-T3 (above), but for video features the Lumix GH5 is still a great choice.

Read our full review: Panasonic Lumix GH5 review

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Here's where things get super specialist. But if you know your stuff then the GH5S will get your salivating at its video prowess.

The GH5S has a lower-resolution sensor than the GH5 (above), as it's designed with video in mind. That sensor offers dual native ISO, which can deliver a far cleaner image at higher ISO settings - which is great for nighttime and low-light work.

There's also no image stabilisation system within the camera, which pros with rigs will prefer to avoid any "jumping" that can happen when such a system is present.

It's hard to call the Lumix GH5S a consumer product, but for higher-end users this will be the small-scale, affordable and capable 4K product they've been waiting for.

Read our full preview: Panasonic Lumix GH5S initial review

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The Sony A9 is a mirrorless camera like no other, although it's not a true "mirrorless", as its SLT (single lens translucent) definiton attests.

But let's not get stuck down too much regarding the camera's technological make-up, because when it comes to ticking all the pro-level boxes, the A9 has so much right.

In full flow, it offers 20 frames per second (fps) with no live view black-out, phase-detection AF that covers virtually the whole frame, and a generally reliable Lock-On tracking AF. To back-up this class-leading performance, Sony also has one of the best lens line-ups for sports and wildlife photography.

In terms of image quality the A9 delivers exactly what we would expect: it's a camera that's able to make great images in both bright and low-light conditions, particularly excelling when the conditions are tough.

It's so good, it asks questions of the DSLR elite (the Nikon D5 and Canon EOS 1D X II are no longer as safe as they once were) and still leaves a big question hanging on the forthcoming Nikon, Canon and Panasonic full-frame mirrorless systems.

Read our preview: Sony A9 initial review

Writing by Mike Lowe.