What is a DSLR camera?

What is a DSLR camera and what sets it apart from mirrorless and point-and-shoots?

What is a DSLR camera
Hillary Grigonis/Digital Trends
What is a DSLR camera? If you’ve been asking yourself this, you’ve come to the right place. We’re going to break down everything you need to know to understand what a DSLR camera is, how it works, and what sets it apart from the likes of mirrorless and point-and-shoot cameras.

Defining a DSLR camera

In the most literal sense, a DSLR camera is a digital single-lens reflex camera. What this means is inside the camera’s body is a mirror that reflects the light coming from the lens and sends it through a prism (in higher-end DSLRs) or a series of mirrors (usually in lower-end models) and finally to the optical viewfinder. This is how you can see what you’re shooting, right through the lens.

When the shutter is pressed, the mirror inside the camera flips up — which is where the term reflex comes into play — and sends the light coming through the lens directly to the sensor instead of the viewfinder.

The advantage of this setup, compared to that of a mirrorless or point-and-shoot camera, is that you can see, in real-time, the exact scene you’re going to capture. There’s no lag, as there tends to be with point-and-shoots and mirrorless cameras where the sensor has to transfer what it’s seeing to a separate digital display elsewhere on the camera. On the downside, you can’t preview your exposure settings through the viewfinder the way you can on a mirrorless camera. (If you haven’t gathered by now, mirrorless cameras are so named because they don’t have a DSLR’s reflexing mirror.)

Another, less talked about advantage is that DSLRs have exceptional battery life because the optical viewfinder draws very little power. Beginner models, like Canon’s EOS Rebel T7i, are usually good for at least 600 shots, while professional models, like Nikon’s 45-megapixel D850, have batteries that can last well over 1,000 exposures.

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A cut away view of Nikon’s D800 camera.

Crop vs full-frame

One of the more confusing elements of DSLRs is the sensor. While DSLR camera sensors are measured in megapixels, like all digital cameras, not all sensors are the same physical dimensions. There are two main sensor types offered by DSLR manufacturers: full-frame and APS-C (often called “crop-frame”).

Explained in the most simple terms, the sensor inside a full-frame camera is the size of a standard 35mm film negative, and this is where the term full-frame comes from. APS-C sensors are about half the size of your standard 35mm negative and, as a result, create what’s called a crop factor.

We have a full explainer on crop factors, but the long and short of it is, if your camera’s sensor has a 1.5x crop factor, a 50mm lens will have the roughly the same field of view as a 75mm lens would have attached to a full-frame camera. This added “zoom” is nice for when you want a little extra reach with your telephoto lens, but means you can’t get as wide of a shot with a wide-angle lens as you would on a full-frame camera.

Most manufacturers make lenses specific to both full-frame and APS-C models, and while all brands allow you to use full-frame lenses on crop-frame bodies, it’s not generally recommended to go the other way around. Some brands, like Canon, don’t even allow it, but on brands that do, like Nikon, using a crop lens on a full-frame body won’t use the entire sensor area and will thus require the image to be cropped significantly.

Bigger is better

Compared to point-and-shoot cameras, even the smallest of DSLR cameras are much larger in comparison. The increase in size makes them a little less compact for carrying around, but means an increase in image quality and speed.

Since DSLR cameras use larger sensors, they tend to offer much better image quality, especially in low-light situations. This is because each individual pixel on the sensor can be larger in size compared to a point-and-shoot camera with the same amount of megapixels. When a pixel is larger, it can capture more light with less digital noise, leading to a clearer image, even in relatively dim lighting conditions.

Autofocus is also an area where DSLRs beat out even the best point-and-shoots. Autofocus technology inside DSLRs is not only faster, but generally provides much better continuous performance and subtract tracking, which is important for shooting any type of moving subject. The quality of a lens also affects how fast and accurate the autofocus is, but generally speaking, there’s no comparison.

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Canon 77D camera with 18-55mm zoom lens attached Daven Mathies/Digital Trends

Interchangeable lenses

One of the biggest advantages of a DSLR camera over a point-and-shoot camera is the ability to attach different lenses to it.

As you may have experienced with your phone or point-and-shoot, sometimes the built-in lens just isn’t enough, whether you want to fit more in the frame or want a little more reach for far-away subjects. With a DSLR camera, it’s as simple as swapping out lenses. Switching lenses is usually as simple as pressing a small button on the frame of the camera, and giving the lens a little twist and pull. A huge variety of lenses exists, from wide-angle models for landscapes to super-telephotos for sports and wildlife to large aperture portrait lenses that create that creamy smooth background blur.

Each camera manufacturer has its own proprietary mounting system and accompanying lenses. Third party lens manufacturers, such as Sigma, Tamron, and many others, tend to offer their lenses in multiple mount types to accompany all photographers.

If you happen to have lenses from old film cameras sitting around the house, odds are you can even mount those to a DSLR with the help of adapters, such as those made by Fotodiox. So don’t feel like you have to drop a lot of money on lenses to make the most of a DSLR camera.

Mirrorless cameras also have the ability to change lenses, and are generally more compact than DSLRs. That said, DSLR cameras have been around for a much longer period of time, so there tends to be more lens options with DSLR cameras than mirrorless cameras, particularly from third parties.

Canon EOS 80D
Jessica Lee Star/Digital Trends
Jessica Lee Star/Digital Trends

Accessories galore

Another strength of DSLR cameras is the ability to use a great deal of accessories and attachments with them. Most any DSLR includes what’s called a hotshoe. This mount on top of the camera can be used as a mounting point for external flashes and even trigger wireless flashes when used with transmitters, such as Pocket Wizards.

DSLR cameras also have a slew of ports for attaching various adapters, trigger systems, external monitors, microphones, wired flashes, and even GPS modules. This versatility makes it easy to customize the camera to fit your exact needs, whether you’re in a studio or on-location in the Himalayas.

New accessories are popping up every day and with each new generation of DSLR cameras comes a new line of accessories to make the most of the device’s technology.

Wrapping it up

Is a DSLR camera right for you? That’s up for you to decide, but hopefully this explainer can help you better answer that question. If you need more help, we have a guide on how to choose a  that best fit your needs, as well as a collection of the best digital cameras of 2017 and the best DSLR cameras you can buy.