Mirrorless vs DSLR cameras: 10 key differences

So you want to get into photography and are looking for a decent camera that you can build a system around?  

A few years ago that was easy question to answer – you had to buy a DSLR. But then in 2009 Olympus launched its first mirrorless camera, the Pen E-P1, and everything changed.

Like DSLRs, mirrorless cameras (also known as CSCs or compact system cameras) allow you to change lenses, but as the name might suggest, the don't feature a complex mirror system like DSLRs do. 

This means that they can in principle be smaller, lighter and mechanically simpler. They can also just like super-sized compact cameras to use, whereas DSLRs are a bit of a jump from a regular compact.

Enthusiasts and pros, however, have taken a bit of convincing on the merits of mirrorless cameras. With no mirror, there's no optical viewfinder, with models either relying on the rear screen or featuring electronic viewfinders, while there have been concerns over image quality, features and handling.

Perhaps most importantly, compared to established DSLR systems, the lens ranges of these mirrorless systems isn't as extensive. 

With a raft of new mirrorless cameras and growing lens ranges, 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 be a help for big lenses (and big hands)
  • CSC: Yes, they are smaller and lighter, but the lenses in some cases can be just as big as a DSLR's

Small size is one of the big selling points for mirrorless cameras, but it doesn't always work out that way because what you actually have to take into account is 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 can get a nice slim body but a fat, heavy lens on the front. 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.

Panasonic and Olympus cameras have an advantage here. The Micro Four Thirds sensor format is smaller (which many photographers don't like) but this means the lenses are smaller and lighter too (which many do), delivering a much more compact system all round.

Interestingly, some higher end mirrorless cameras are now growing in size as they take on more features and manufacturers respond to feedback from photographers who want larger grips, while entry-level DSLRs are shrinking to compete with the smaller footprint of similarly priced CSCs.

  • DSLR: Canon and Nikon have a massive lens range for every job, while Sony and Pentax are not far behind
  • CSC: Olympus, Panasonic and Fujifilm have good ranges, Sony is catching up, others are patchy

If you want the widest possible choice of lenses, then a Canon or Nikon DSLR is possibly the best bet thanks to their huge range of optics – they both have 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. 

Mirrorless cameras are gaining ground though. Because Olympus and Panasonic use the same lens mount and have been established the longest, the range of Micro Four Third lenses is the most comprehensive. 

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 is very good. Sony offers some really nice high-end optics, but it could do with introducing more glass, especially at focal lengths beyond 200mm.

  • DSLR: Many still prefer an ‘optical’ view for its clarity, natural look and lag-free viewing
  • CSC: Others prefer to see a digital rendition of the scene as the camera will capture it

All DSLRs, even the cheapest, come with an optical viewfinder because it's an integral part of the DSLR design. However, quite a few compact system cameras 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.

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

Electronic viewfinders are advancing in leaps and bounds, so the latest rarely show any pixelation or 'granularity', though there can often be a slight but visible 'lag' if you move the camera 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.

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 straight after it's been captured.

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: Still better, on the whole for tracking fast subjects, but weak in live view mode
  • CSC: Full time live view AF means faster shooting when using the LCD screen

DSLRs use fast and efficient 'phase detection' autofocus modules mounted below the mirror in the body, but these 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 much slower contrast AF system using the image being captured by the sensor.

The latest Canon DSLRs (such as the EOS Rebel T7i / EOS 800D, EOS 80D and EOS 5D Mark IV) though include the company's 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 CSCs.

CSCs have to use sensor-based autofocus all the time. Most are contrast AF based although, but these tend to be much faster than equivalent contrast AF modes on DSLRs, partly due to the fact the lenses have been designed around this system. 

More advanced CSCs have advanced 'hybrid' AF systems combining contrast autofocus with phase-detection pixels on the sensor, with the likes of the Fujifilm X-T2 and Olympus OM-D E-M1 Mark II really impressing with not only their speed, but with the accuracy at which they can lock on and follow a moving subject – the one area where DSLRs have, until now, had a clear advantage.

  • DSLR: The best DSLRs can no longer match the speeds of the best CSCs
  • CSC: The mirrorless design makes it easier to add high-speed shooting

You need a fast continuous shooting mode to capture action shots, and compact system 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 Olympus OM-D E-M1 Mark II can shoot at staggering 60fps. 

That's not quite the full story though – while the Canon will blitz away at this rate with continuous focus tracking in action, the Olympus will use an electronic shutter to achieve this and the focus will be fixed. That said, activate the mechanical shutter on the Olympus and 10fps is possible with full focus tracking. 

Panasonic, meanwhile, is pioneering the use of 4K video to capture 8-megapixel images at 30 frames per second.

  • DSLR: Massively popular with pros but, arguably, only because DSLRs got there first
  • CSC: 4K video becoming more common, better live view AF – this looks like the future

DSLRs were the first to offer professional HD and Full HD video, together with a vast range of lenses and other accessories, and pros prefer systems with solid, long-term support.

This means that most pros shooting video use a DSLR, but that's changing as mirrorless cameras advance and offer a wealth of video features that match DSLRs or in some areas, better them.

4K capture is a more common feature for starters on mirrorless cameras, while DSLRs have been slow to offer this functionality. There's also the efficient live view autofocus and processing power, while there's a growing range of adapters and accessories out there to offer users a complete system.

Panasonic has carved out a niche for itself with the Lumix GH5, 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 cameras
  • CSC: They match DSLRs feature for feature, often going a step or two further

In terms of photographic features and controls, DSLRs and CSCs 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 CSCs.

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

  • DSLR: DSLRs use the latest and best state of the art APS-C or full-frame sensors
  • CSC: They 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 DSLR, the 50MP chip nestled inside the Canon EOS 5Ds, but the 42.5MP Sony Alpha A7R II isn't far behind.

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

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.

Nikon uses a 1-inch sensor in its Nikon 1 series cameras, but this is a much smaller sensor size that's yet to cut much ice with experts. That is for interchangeable lens cameras at least, as the 1-inch sensor has proved incredibly popular in premium compact cameras like the Panasonic Lumix LX10 / LX15.

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

  • DSLR: 600-800 shots is average, better models can shoot over 1,000 shots on a charge
  • CSC: Much weaker, and typically around 300-400 shots. You’ll need spare batteries

Battery life comparisons might not be exciting, but they are important when the differences are as great as this. The Nikon D7200 DSLR, for example, can take 1,100 shots on a single charge, while the Fujifilm X-T2 CSC, a close match on paper, can only shoot 340 photos before the battery expires. This pattern is repeated across the range of DSLRs and CSCs.

It's not clear why. 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.

Apparently not, though, and 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: You get more for your money with a cheap DSLR than a cheap CSC
  • CSC: Cheap CSCs don't have viewfinders; those that do cost a 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 D3300 DSLR has just about the best APS-C sensor currently on the market, an optical viewfinder (of course), decent manual controls and 700-shot battery life.

Its nearest rivals on price in the compact system 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 just 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 quality
  • CSC: Smaller, technically more advanced and arguably the way forward

The technical differences between DSLRs and CSCs 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 compact system 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, a cheap DSLR gives you more than a cheap compact system 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.

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