If you want to upgrade from smartphone or point-and-shoot cameras to an interchangeable-lens camera, you have two main choices: DSLRs or so-called "mirrorless" cameras. Both of these camera types do essentially the same thing, but each type has its strengths and weaknesses.
Single lens reflex (SLR) cameras have been around for more than a 100 years. Like their film-based predecessors, today's digital SLRs (DSLRs) use a mirror to divert the light from the lens into a viewfinder so you see exactly what the camera sees. When you take a picture, this mirror flips up out of the way, a shutter in front of the image sensor opens, and the sensor captures the image.
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Mirrorless cameras, as the name suggests, don't need a mirror. Instead, the light passes through the lens and falls right onto the image sensor, as it does in point-and-shoot and phone cameras. To preview the image before you press the shutter button, you look at a screen on the back of the camera, or into a viewfinder with an electronic screen.
So which is better? We looked at the pros and cons of the two types to see how they compare, and which is the best for each category:
Size & Weight
DSLR camera bodies are comparatively larger, as they need to fit the mirror and shutter mechanisms. The body of the $550 Nikon D3300 (see review), our top entry-level DSLR recommendation, is a rather bulky 3 inches deep. The body with the 18-55mm kit lens weighs about 1 pound, 7 ounces. Midrange DSLR models quickly get heavier as the bodies get more robust, though, with a $1,600 Canon 70D and 18-135mm lens weighing in at a hefty 2.6 pounds.
Without a mirror mechanism, a mirrorless camera body can be smaller than a DSLR, and the construction is simpler. The Samsung NX300 (comparable in performance to the Nikon D3300 and also one of our top recommended models) has a body just 1.6 inches thick and weighs just over 1 pound with its 18-55mm kit lens. Some mirrorless models, like the Nikon 1 family of cameras, are the size of larger point-and-shoot cameras. Most mirrorless cameras still use a mechanical shutter, as it allows faster shutter speeds, because it is easier to create a shorter shutter speed by using a physical shutter to control light than it is electronically.
This smaller and lighter design of a mirrorless camera means that you carry around less weight, and can get more into a small camera bag: an important factor when you start using more lenses and other accessories.
Winner: Mirrorless camera
When you are looking through the viewfinder, DSLRs use the mirror mechanism to divert light into a dedicated focus sensor that employs a process called phase detection. The sensor measures the convergence of two light beams to quickly snap the lens into focus.
Mirrorless cameras used to be restricted to a slower technique, called contrast detection, where the image sensor looks for a sharp, high-contrast edge on an object and repeatedly moves the lens until the edge is as sharp as possible. (Virtually all DSLRs also use contrast detection when shooting video or stills in live view mode with the mirror raised.) Contrast detection is especially slow in low light and with moving subjects..
However, many recent mirrorless cameras, like the Samsung NX300 and Sony A6000 (see review), have phase detection built into their image sensors, so they can use both methods (often called hybrid AF). This makes them nearly as fast as a DSLR at focusing. Although DSLRs are still usually a little faster, mirrorless cameras are quickly catching up, and there is increasingly little difference between them.
Winner: DSLR (by a hair)
The upside of the DSLR viewfinder is that you can see the image directly, previewing exactly what the image sensor will capture.
The downside of mirrorless cameras is that they have to capture a preview of the image to display on the LCD screen. This preview can often be jerky or hard to see, especially on a cheap LCD in bright daylight. In low light, the preview can appear grainy.
Some mirrorless models mimic DSLRs by embedding a small LCD or OLED screen in what's called an electronic viewfinder (EVF). These more expensive models, Fujifilm X-E2 (see review) and the Olympus OM-D E-M10 (see review), offer a DSLR-like experience, because a viewfinder is easier to use in dark or cramped locations. However, the electronic preview these cameras offer have the same problem as the screen: grainy, noisy images that are hard to see in low light.
Electronic viewfinders do have some benefits, though. They can preview exactly what the photo will look like, for example in terms of color, because they capture data right from the sensor.
Conversely, DSLRs mimic mirrorless cameras when they engage live view. They raise the mirror to expose the image sensor sensor in order to put a preview of the shot on the camera screen.
All modern removable-lens cameras include image stabilization, in which the camera reduces the blur in photos (generally at slow shutter speeds) by compensating for your shaky hands. Most interchangeable lens cameras, especially DSLRs, do this by shifting a small part of the lens in the opposite direction or directions that the camera moves. Others shift the image sensor, which enables image stabilization with any lens, even vintage models that often fit on new cameras.
Some mirrorless cameras can shift both a lens element and the image sensor — a combination that can be more effective than either of these methods alone. On recent models, the differences between most DSLR and mirrorless image-stabilization systems are minimal.
Early mirrorless cameras used to offer lower-quality images than DSLRs, with more noise (graininess) and worse color, because they used smaller image sensors that captured less light. But the manufacturers of mirrorless cameras have found ways to reduce the noise, using better (and often bigger) sensors and more powerful image processors, and now there is no noticeable difference in image quality in most consumer models. High-end DSLRs use very large sensors called "full frame" sensors that have given them an edge at the high end, but that is changing. The Sony Alpha A7 (see review) series has brought full frame to the mirrorless world as well, and other models will be coming soon.
While there are far more high-end DSLRs than mirrorless cameras, in the mainstream consumer range, the quality gap has been bridged.
Both types of cameras can handle video, but mirrorless cameras are better suited for two reasons: focus and video quality. When capturing video, DSLRs flip the viewfinder mirror up and have to use the contrast-detection focusing method, which means slower focusing, creating the familiar sharp-blurry-sharp effect in the video when the subject moves and the camera has to refocus. The Canon 70D (see review), with phase detection on its sensor, is the one notable exception. Mirrorless cameras, by comparison, are built with focus sensors on the imaging chip, often using both phase and contrast focusing, which is quicker.
Many DSLRs also have limitations on how long they can shoot video for, often restricting clips to 10 minutes. The Nikon D3300, for instance, can shoot only 10- or 20-minute clips, depending on the quality setting used. That's either because the image sensor heats up, and you then have to let it cool, or because there is a maximum file size that the camera can store on a memory card, and it needs to stop recording to start a new file.
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Mirrorless cameras are built with extra cooling to stop this overheating, and most can shoot for much longer, although some still have the file size limitation. The Olympus OM-D E-M10 can shoot videos of up to 29 minutes, for instance, as long as the video files stay smaller than 2GB in size. This might not be a concern if you are just shooting short videos or clips, but it can be a problem if you want to shoot a whole school play or similar.
As in other cases, the exception is at the higher-end, simply because DSLR makers have invested more money and time in top video performance in models such as the Canon 70D and 5D Mark III. But in mainstream cameras, mirrorless models offer a better experience.
Image & Video Playback
When it comes to showing an image you have just captured, both camera types can use either their LCD screen or an HDMI output to your television. Although the bodies of mirrorless cameras are smaller, most have the same 3-inch LCD screen size commonly found on DSLRs. Many DSLR and mirrorless models now also include Wi-Fi, which allows you to connect them to smartphones via an app for sending images to websites like Facebook. Some of these apps also allow you to remotely control the camera and even see an image preview over the wireless connection.
Lenses & Accessories
If you are looking to purchase a new interchangeable-lens camera, you are buying into an entire ecosystem of lenses, flashes and other accessories that go with it. You can't use a Micro Four Thirds-format mirrorless camera lens on a DSLR camera body, for example, or a Sony lens on a Nikon (whether DSLR or mirrorless). So, when choosing a camera, you need to consider the range of lenses available for it.
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Choosing a DSLR gives you access to a plethora of lenses — from a number of manufacturers — ranging from cheap and satisfactory to professional and wildly expensive. By contrast, most mirrorless models take only a small selection of lenses from the camera maker, though the selection is slowly growing.
The proprietary mirrorless systems from manufacturers like Sony (A series), Pentax (Q cameras) and Samsung (NX series) have the fewest lenses, because these companies have only recently introduced mirrorless models. Samsung offers only about a dozen NX lenses, for instance, while Nikon has hundreds available for its DSLRs. Micro Four Thirds mirrorless cameras have the widest selection because they have been around the longest and are made by several companies — Olympus and Panasonic make the cameras, and lenses are made by Olympus, Panasonic, Sigma, Tamron and others.
You can generally purchase adapters to use DSLR-size lenses on a mirrorless camera by the same manufacturer. But that often comes at a price of altering the focal length and zoom characteristics and sometimes disabling functions such as autofocus.
So, which camera type is the best pick overall? That depends on your priorities. If top image quality and speed are most important for you, regardless of weight or bulk of the gear, choose a DSLR for its consistent high quality (as mirrorless cameras are still hit-or-miss) that is generally available at a lower price for entry-level models. And if you are prepared to spend upward of $1,200 or so, DSLRs still outperform mirrorless cameras on the high end. DSLRs also offer a wider lens selection in most cases.
But most mirrorless cameras have enough lens options for most shooting situations, and focus speed and image quality are improving. Therefore, mirrorless cameras are the best choice if you want to take a high-quality camera everywhere without getting weighed down.