Mirrorless vs DSLR: introduction
So you want a decent camera that takes interchangeable lenses? A few years ago that was easy – you had to buy a DSLR. But then in 2009 Olympus launched its first mirrorless camera, the Pen E-P1, and everything changed.
Though it didn't change overnight. Mirrorless cameras are great in principle because they're smaller, lighter and mechanically simpler. They're also just like supersized 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 – first, that the image quality is good enough to match a DSLRs; second, that the features and handling are comparable; third and most important, that these cameras have, or will have, a proper range of lenses to match those already available for DSLRs.
So 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.
1. Size and weight
- DSLR: Yes, they're fat and chunky, though this can be a help for big lenses (and big hands)
- CSC: Yes, they are smaller and lighter, but the lenses (mostly) are 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 APS-C mirrorless cameras because you can get a nice slim body but a fat, heavy kit lens. Some now come with retractable or power-zoom 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).
- DSLR: Canon and Nikon have a massive lens range for every job, and Pentax is not far behind
- CSC: Olympus, Panasonic and Sony have good ranges, Samsung 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 best, but mirrorless cameras are gaining ground. Sony mirrorless cameras are well supported now – though more fast prime lenses and constant aperture zooms would help – and Panasonic and Olympus use the Micro Four Thirds format, which now has a large and established lens range behind it.
- 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, many 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.
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.
- 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.
Some Canon DSLRs, notably the EOS 70D and EOS 7D Mark II (Dual PIxel AF) and EOS 750D and 760D (Hybrid CMOS AF) have hybrid AF using phase-detection pixels built into the sensor. This is designed to give faster autofocus in live view mode to close the gap on CSCs, but this technology is currently the exception for DSLRs rather than the rule.
CSCs have to use sensor-based autofocus all the time. Most are contrast AF based although, for whatever reason, these are much faster than equivalent contrast AF modes on DSLRs. More advanced CSCs have advanced 'hybrid' AF systems combining contrast autofocus with phase-detection pixels on the sensor, and the best are now so fast that they're getting pretty good at locking onto and following moving subject – the one area where DSLRs have, until now, had a clear advantage.
5. Continuous shooting
- 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 can shoot at 12 frames per second, but the mirrorless Samsung NX1 can shoot at 15fps. 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
Most pros shooting video use a DSLR, but that says more about the rather conservative professional market than the technology. 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.
But that was then. The industry is waking up to the potential offered by mirrorless technology, including 4K video (still yet to appear on consumer DSLRs), efficient live view autofocus and high-speed data readout and processing. The Panasonic GH4, for example, has had a big impact as a hybrid stills/video camera that's equally good in both roles, rather than a stills camera adapted to shoot video.
- 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. They all offer full manual control over exposure and focusing and can shoot raw files as well as JPEGs. 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 cheaper compact system cameras don't.
8. Image quality
- 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 smaller cameras
There's nothing to choose here either. Currently, the highest resolution is in a DSLR, the 50Mp Canon EOS 5Ds, but the 42.5Mp Sony 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 good and much cheaper – and you can get these sensor sizes 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. 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.
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.
9. Battery life
- 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 Fuji X-T1 CSC, a close match on paper, can only shoot 350 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.
- 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 good deal more
You might hope that the simpler design of a compact system camera would make them cheaper to buy, but that's not the case. If you want a fully-featured, 'proper' camera for the least money, then a DSLR is the cheapest option.
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.
In fact, the cheapest CSC with a viewfinder at the time of writing is the 16Mp Olympus OM-D E-M10, which currently sells for around 30% more than the Nikon D3300 – and 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.
Mirrorless vs DSLR: the verdict
- 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. 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.
For novices and those on a budget, a cheap digital SLR 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 for the old DSLR format to stick around.