Mirrorless vs DSLR cameras: 10 key differences

So you want to get into photography and you're looking for a decent camera that you can build a system around. Do you go for a mirrorless camera or a DSLR?

At one point, that was easy question to answer: you had to buy a DSLR if you wanted to get creative with your photography. But in 2008 Panasonic launched the world's first mirrorless camera, the Lumix G1 – and everything changed.

Like DSLRs, mirrorless cameras – also known as CSCs or compact system cameras – allow you to change lenses, but, as the name suggests, they don't feature a complex internal mirror system like DSLRs do. 

This means they can be smaller, lighter and mechanically simpler than an equivalent DSLR. It also means they can be as approachable as compact cameras in use, whereas most DSLRs are something of a jump from a regular compact camera.

With no mirror, there’s no optical viewfinder. That means that mirrorless cameras rely on either the rear LCD screen or electronic viewfinders for image composition.

Enthusiasts and professionals, however, have traditionally taken a bit of convincing on the merits of mirrorless cameras. The absence of an optical viewfinder, together with streamlined controls and limited lens range for most systems, used to be a turn-off for a lot of experienced photographers. 

That's all changing though. As manufacturers widen the lens range and options available, lens choice is becoming less of an issue. A raft of new mirrorless cameras have also now arrived to tempt photographers away from the more traditional DSLR, with performance and image quality in some instances bettering DSLR rivals for a similar price. 

But have mirrorless cameras done enough to be genuine DSLR rivals? Or, more to the point, are they already better? To help you decide, here are the key differences and what they mean for everyday photography.

DSLR: Can be big and bulky, though this can help when shooting with big telephoto lenses (and big hands)Mirrorless: These are generally smaller and lighter, but the lenses in some cases can be just as big as those for DSLRs. Some mirrorless cameras are as big as equivalent-level DSLRs

One of the big selling points for mirrorless cameras has been their small size, but it doesn't always work out that way. The reason? You have to take into account the size of the camera body and lens combination. 

This is a problem for mirrorless cameras with either full-frame or APS-C-sized sensors because you might be able to get a small body but the compatible lenses might be large and heavy. Some models now come with retractable, or power-zoom, 'kit' lenses, but that doesn't help when you have to swap to a different type of lens.

Sensor sizes explained: what you need to know

Panasonic and Olympus cameras have an advantage here; the Four Thirds sensor format inside its Micro Four Thirds models is smaller than APS-C and full-frame types. Many photographers don't like this, but it means that lenses are often smaller and lighter too, which helps to deliver a much more compact system all round.

Interestingly, some higher-end mirrorless cameras like the Sony Alpha A7R IV, Olympus OM-D E-M1X and Canon EOS R, are now growing in size as they take on more features, and as manufacturers respond to feedback from photographers who want larger grips.

At the end of the scale, entry-level DSLRs are shrinking to compete with the smaller footprint of similarly priced mirrorless cameras. Nikon's D3500 and Canon's EOS Rebel T7 / 2000D are painfully small and light, making them less of a burden to carry around.

DSLR: Both Canon and Nikon have a massive lens range for every job. Pentax also has many bases covered, and contributions from many third parties only adds more options to each systemMirrorless: Lens ranges for even more established lines are still developing, but many options are now covered. The most recent is on newer systems from the likes of Canon, Nikon, Panasonic and Fujifilm's medium format line, which are still getting off the ground

If you want the widest possible choice of lenses, a Canon or Nikon DSLR is possibly your best bet. Each has an extensive range of lenses to suit a range of price points, as well as excellent third-party support from the likes of Sigma and Tamron. 

While Canon and Nikon have both had decades to build-up and refine their lens line-up – Nikon's lens mount is unchanged from 1959, for example – the first mirrorless camera only appeared 11 years ago. Mirrorless cameras are, however, certainly gaining ground. 

Because Olympus and Panasonic use the same Micro Four Thirds lens mount and have been established the longest, the range of Micro Four Third lenses is the most comprehensive, offering a broad range of optics, from ultra wide-angle zooms to fast prime telephoto lenses. 

Fujifilm's lens system is growing all the time, with some lovely prime lenses and excellent fast zoom lenses. Even the 18-55mm 'kit' lens that comes with many of its cameras as standard is very good. There are still a few gaps in the range, but Fujifilm is definitely working hard to deliver a comprehensive, high-quality range of lenses.

Sony offers some really nice high-end optics that are designed for its full-frame line of cameras like the Alpha A7 III, while its just recently launched a mighty FE 600mm f/4 GM OSS telephoto prime lens too. It now offers a relatively healthy selection for both its APS-C and full-frame cameras.

Both Canon and Nikon have recently launched full-frame mirrorless cameras to run alongside each company's DSLR range. At the moment, the dedicated optics for each are limited to a handful of lenses, but many more are promised. Not only that but both Canon and Nikon offer affordable adapters that allow you to use lenses designed for DSLRs (though in some cases, with restrictions).

The most recent change here is the introduction of the L-mount alliance, a venture that unites Panasonic, Sigma and Leica. The three companies have pledged to develop products that can be used in conjunction with those from the other manufacturers, which should help the line to develop quickly.

DSLR: Many photographers still prefer an 'optical' view for its clarity, natural look and lag-free viewing. These are standard on DSLRsMirrorless: Others prefer to see a digital rendition of the scene as the camera will capture, and electronic viewfinders on many mirrorless cameras allow this. Some of the most recent examples are very high in quality

All DSLRs, even the cheapest, come with an optical viewfinder because it's an integral part of the DSLR design. Many entry-level mirrorless cameras, on the other hand, don't have viewfinders at all, so you have to use the rear LCD to compose photos, which doesn't always work so well in bright light.

Mirrorless cameras with viewfinders cost more, and these are electronic rather than optical viewfinders. That means they display the image directly from the sensor readout and not via an optical mirror/pentaprism system.

Electronic viewfinders are advancing at a fast pace, and the latest rarely show any graininess that was an issue in earlier generations, though there can often be a slight but visible lag if you move the camera really quickly.

The advantage of electronic viewfinders is that they can display a lot more information than an optical viewfinder, including live image histograms, for example. They can also simulate the digital image the camera will capture, so you don't get any horrible surprises when you review your image as it's exactly what you're seeing.

This simulation is not always perfect, however, and many photographers prefer to see the world with their own eyes as they compose the image and check the digital version on the LCD once it's been captured. They're also easier to use in low light.

This will come down to personal preference; get one of the latest high-end mirrorless cameras with a large magnification, large resolution electronic viewfinder, and you'll be hard pressed to find fault with it.

DSLR: Used to have a clear advantage, but not quite as clear-cut now. On the whole they're better for tracking fast subjects, but can be weak in live viewMirrorless: While entry-level models may struggle, many mirrorless cameras now have hybrid contrast- and phase-detect AF systems, which fare much better. Some systems are as reliable as those on DSLRs, if not more so

DSLRs use fast and efficient 'phase-detection' autofocus modules mounted below the mirror in the body. This system can be incredibly fast at focusing and tracking subjects, with cameras like the Nikon D850 and Canon EOS-1D X Mark II offering an incredibly sophisticated system. 

The trouble is that these systems only work while the mirror is down. If you're using a DSLR in live view mode, composing a picture or video on the LCD display, the mirror has to be flipped up and the regular AF module is no longer in the light path. Instead, DSLRs have to switch to a slower contrast-detect AF system using the image being captured by the sensor.

Many of the latest Canon DSLRs (such as the EOS Rebel SL3 / EOS 250D and EOS 6D Mark II), however, include the company's brilliant Dual Pixel CMOS AF that uses phase-detection pixels built into the sensor. This is designed to give faster autofocus in live view mode to close the gap on mirrorless cameras – and it works very well indeed.

Mirrorless cameras have to use sensor-based autofocus all the time. Most are contrast-detect AF based, but these tend to be much faster than equivalent contrast AF modes on DSLRs.

More advanced mirrorless cameras have advanced hybrid AF systems that combine contrast-detect with phase-detect AF from the sensor. The likes of the Fujifilm X-T30, Panasonic Lumix G9, Sony Alpha A7 III and Olympus OM-D E-M1X impress not only with their speed, but also the accuracy with which they can lock on and follow a moving subject. This is one area where DSLRs have traditionally had a clear advantage.

DSLR: The best DSLRs can no longer match the speeds of the best mirrorless camerasMirrorless: The mirrorless design makes it easier to add high-speed shooting and even cheaper models have relatively fast burst speeds

You need a fast continuous shooting mode to capture action shots, and mirrorless cameras are streaking ahead here, partly because the mirrorless system means there are fewer moving parts and partly because many models are now pushing ahead into 4K video – this demands serious processing power, which helps with continuous shooting too.

To put this in perspective, Canon's top professional DSLR, the EOS-1D X Mark II, can shoot at 14 frames per second, but the mirrorless Panasonic Lumix G9 and Sony Alpha A9 can both shoot at a staggering 20fps. 

You have to be a little careful though when looking at the spec. Some mirrorless cameras will boast even higher frame rates than this (in some cases, up to 60fps), but will have to use an electronic shutter to achieve this and focus will be fixed from the first shot. Not great if you're planning on tracking a moving subject, or under some types of artificial light where banding can occur without the use of a mechanical shutter.

You've also got to be realistic about what kind of burst shooting speeds you are going to need; shooting at 60fps means you'll fill up a memory card pretty quickly, and you'll have to spend a lot of time trudging through a multitude of images to find that 'one' shot. That said, with even entry-level mirrorless cameras offering faster burst shooting speeds than most DSLRs, mirrorless cameras certainly have the edge if this is your priority.

DSLR: Once massively popular with pros but getting overtaken by mirrorless rivalsMirrorless: 4K video is now standard on all but the cheapest mirrorless cameras

DSLRs were the first to offer professional HD and Full HD video capture, which together with a vast range of lenses and other accessories, was instantly a hit with pros and video makers.

But the shift has certainly been in mirrorless cameras favor in recent years, offering a wealth of video features that most DSLRs can't match.

4K capture is a more common feature for starters on mirrorless cameras, while DSLRs have been slow to offer this functionality. 4K video capture is almost unheard of in entry-level DSLRs, and only a handful of models further up the chain offer this.

There's also the efficient live view autofocus and processing power offered by mirrorless cameras, while the growing range of adapters and accessories out there offer users a more complete system.

Panasonic has carved out a niche for itself with the Lumix GH5 and Lumix GH5S, offering a hybrid stills/video camera that's loved by enthusiast photographers and professional cinematographers, while Sony has opted for a similar approach with the Alpha A7S II

DSLR: Even entry-level models have full manual controls, and DSLRs are powerful camerasMirrorless: They match DSLRs feature for feature, often going a step or two further

In terms of photographic features and controls, DSLRs and mirrorless cameras are hard to split here. 

They all offer full manual control over exposure and focusing and can shoot raw files as well as JPEGs, allowing you to get the best image quality possible. In any one sector, such as entry-level cameras, enthusiast or pro models, the control layouts and capabilities are pretty similar. Entry-level DSLRs tend to hide away the manual controls under a layer of automation, but it's the same for mirrorless cameras.

Keep in mind the point about viewfinders, though – all DSLRs have viewfinders, but often cheaper mirrorless cameras don't.

DSLR: DSLRs use APS-C or full-frame sensors.Mirrorless: They typically use the same sensors, but there are also smaller formats for even smaller cameras.

There's nothing to choose here either. Currently, the highest resolution is in a mirrorless camera, the medium format Fujifilm GFX 100, which has a 102MP sensor. Admittedly, that's not a camera many people can afford, although the cheaper Sony A7R IV mirrorless camera manages 61MP – still a good 11MP more than the closest DSLR, the Canon EOS 5DS and 5DS R.

It's not just about megapixels, though, because the main factor in image quality is sensor size. With the exception of medium format sensors, full-frame sensors are the biggest and offer the best quality, while cameras with APS-C sensors are almost just as good and much cheaper – and you can get either of these size sensors in both DSLRs and mirrorless cameras.

But the compact system camera market offers smaller formats too. The Micro Four Thirds format used by Panasonic and Olympus is smaller than APS-C, but so are the cameras and lenses, so you need to weigh up what's most important to you – size or ultimate image quality.

Overall, then, there's no intrinsic image quality advantage in a DSLR, given that the same sensor sizes are available in mirrorless cameras too.

DSLR: 600-800 shots is average, better models can shoot over 1,000 shots on a charge. Pro DSLRs may offer 2000+ shots per chargeMirrorless: Much weaker, typically around 300-400 shots per charge. Some manage around 600 or 700, although those with a higher battery life will often have either very large batteries or require two

Battery life comparisons might not be exciting, but they are important when the differences are as great as this. 

The very affordable Canon EOS Rebel SL3 / EOS 250D DSLR, for example, can take 1,070 shots on a single charge, while the Fujifilm X-T3 mirrorless camera, a much more advanced model, match on paper, can only shoot 390 photos before the battery expires. This pattern is repeated across the range of DSLRs and mirrorless cameras.

Why's this? DSLR batteries are sometimes larger, though not always, and you might have thought that driving the mirror up and down for each shot would consume more power, and that that LCD display would be used just as much. However, mirrorless cameras will have to power an EVF in most cases as well.

So, this is one area where DSLRs do often have a substantial practical advantage. You'll certainly need an extra battery or two with most mirrorless cameras.

DSLR: The cheapest DSLRs may miss out on some feature like touchscreens and 4K video Mirrorless: Cheap mirrorless cameras often have these but don't have viewfinders; those that do cost more.

You might hope that the simpler design of a compact system camera would make them cheaper to buy, but that's not necessarily the case. If you want a fully-featured, 'proper' camera for the least money, then a DSLR is still the cheapest option – but it's getting a lot closer between the two.

For example, the 24MP Nikon D3500 DSLR has just about the best APS-C sensor currently on the market, an optical viewfinder (of course), decent manual controls and a staggering 1,550-shot battery life.

Its nearest rivals on price in the mirrorless camera market can't match its resolution or its battery life and they don't have viewfinders, but for only a little more the Sony Alpha A6000 packs in an almost identical 24MP APS-C sensor and features a built-in electronic viewfinder. You'll still need to get a second battery though. That said, it's only that cheap because it's been superseded.

Once you get into enthusiast and pro market, however, the differences largely disappear – for any given amount of money you get broadly the same features, performance and power.

DSLR: Sturdy, good value cameras offering old-school handling and top image qualityMirrorless: Smaller, technically more advanced and arguably the way forward

The technical differences between DSLRs and mirrorless camera aren't the only things you need to consider, and may not even be the most important to you. 

The only way to decide once and for all is to pick them up and try them out to see which you prefer. You might prefer the fat, chunky feel and optical viewfinder of a DSLR, or you might prefer the smaller bodies and more precise feel of a mirrorless camera. It'll really come down to what you like to shoot and what the camera can deliver – and pay attention to the lenses offered and accessories available as well.

For novices and those on a budget, an entry-level DSLR gives you more than a cheap mirrorless camera. Further up the price range, it's a close call, but you'd have to say that while some might prefer their handling and their viewing system, there are fewer and fewer technical reasons why a DSLR should be considered the best option for photographers.

Read more: techradar.com

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