Why Do Smartphones Have So Many Cameras, and What Do They Do?

Justin Duino / Review Geek

Smartphones offer multiple cameras to increase your creative choices and improve overall image quality through software. You’re probably using all of your phone’s cameras, even if you don’t realize it.

Modern smartphones contain several cameras, giving you several creative choices when photographing family members, road trips, football games, and more. But chances are, you don’t really understand how these cameras work, and you may feel like you only ever use the “main” camera.

Here’s the good news; you’re already using all of your smartphone’s cameras, even if you don’t know it. And with just a bit of knowledge, you improve your photography skills and pull even more usefulness out of your phone’s giant camera array.

Why Do Smartphones Have Multiple Cameras?

Digital cameras contain a ton of small parts. But the most important components of a digital camera are the image sensor and the lens. While the image sensor dictates resolution and overall photo quality, the lens controls stylistic quirks like field of view or focal length—we’re oversimplifying things here, but that’s the gist of it. (And yes, we’ll explain what these terms mean in a moment.)

Professional DSLR and mirrorless cameras have a built-in image sensor, which cannot be removed. So,  to provide more stylistic freedom for the photographer, DSLR and mirrorless cameras offer an interchangeable lens system. If you need a detailed photo of a faraway subject, just pull out your telephoto lens and snap it to the camera!

Justin Duino / Review Geek

Smartphones are too small and fragile to use interchangeable lenses. So, to mimic the flexibility of a “real” camera, phones offer multiple image sensors, each with their own unique lens.

Phones automatically switch between these cameras while you shoot photos, eliminating the learning curve associated with DSLR or mirrorless cameras (automatic camera switching usually occurs when zooming in or out). That said, you can manually select a lens from your phone’s camera app, similar to how a professional photographer might pull a lens from their bag.

Wide or “Main” Cameras: General-Purpose Shooting

A wide-angle camera has a relatively short focal length, usually between 24mm and 35mm (we’re talking equivalent focal length, by the way). This provides a wide field of view, allowing you to capture larger scenes than you might get with a telephoto lens. Additionally, the short focal length gives you a large depth of field—objects in the foreground and background stay in focus.

Smartphone camera apps always default to the wide-angle lens. So, this is usually referred to as the “main” lens in a smartphone, and as you might expect, it’s the ideal option for most photos.

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That said, wide-angle cameras tend to produce some very “basic” photos. To get around this problem, manufacturers may utilize “computational photography” to enhance image quality or style. Basically, the phone runs your pictures through some software to make the pictures prettier.

The iPhone’s Portrait mode is a great example of “computational photography.” As we mentioned earlier, wide-angle lenses keep the subject and background in focus. But Portrait mode utilizes data from a phone’s telephoto camera (which has a shallow depth of field) to blur the background behind a subject.

It’s also worth noting that, due to technological constraints, the vast majority of smartphone cameras use a fixed-focus lens. This kind of lens cannot be adjusted to magnify an image. So, optical zoom is off the table, and digital zoom (which noticeably reduces photo quality) usually takes its place.

But some smartphones offer optical zoom using a fancy trick—they swap to a different camera, usually one with a 3x telephoto lens. This is one of the biggest motivators behind a multi-lens design. Even if a user doesn’t understand their phone’s cameras, they’ll notice that the zoom function looks better on a new phone.

Telephoto Cameras: High-Quality Zoom

Telephoto lenses are basically the opposite of wide-angle lenses. They have a long focal length between 50mm and 80mm, meaning that they are “zoomed” by default and capture a relatively narrow area of a scene.

As the name implies, a telephoto lens is made to capture faraway subjects. If you need to take a photo of a bird on a tree or a kid in a softball field, you switch to the telephoto lens. This happens automatically when you zoom in on a camera with a telephoto camera, and is usually indicated by a small on-screen icon that shows a zoom ratio of “2x” or “3x.”

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Telephoto lenses have a shallow depth of field. So, while your subject stays in focus, objects in the background (or objects that are very close to the camera) may have a nice natural blur. Surprisingly, this makes the telephoto lens a great choice for portraiture— the narrow FOV helps you frame the subject, while the shallow depth of field gives you a slight (or extreme) background blur.

But this effect is less noticeable in a smartphone’s telephoto camera, where limitations related to sensor size, aperture, and focal length can “cancel out” a shallow depth of field. Unless your background is very far away, you usually need computational photography to achieve background blur when using a smartphone telephoto camera.

We should also note that telephoto lenses can “compress” an image. This is a side effect of the shallow depth of field—the background appears to be “closer” to your subject. It can be a good thing or a bad thing, depending on your sense of style.

Ultra-Wide Cameras: Capture More of a Scene

As you can probably guess, ultra-wide cameras capture an extremely large area of any scene. They can even feel “zoomed out” when compared to your typical wide-angle camera, which is why smartphones usually designate the ultra-wide lens as “0.5x zoom.”

Ultra-wide cameras have a focal length between 16mm and 24mm. This provides an extremely large depth of field. Essentially, everything in your image stays in focus.

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Thanks to its short focal length and large depth of field, the ultra-wide camera is a great option when shooting in nearly any setting. Your phone’s ultra-wide lens is great for landscape photos, but it can also capture a ton of detail in tight spaces, like hallways, city streets, or car interiors.

That said, ultra-wide lenses introduce barrel distortion when shooting at close range. It’s like a lightweight version of the “fisheye” effect—the center of your image pulls forward, while the edges push toward the left and right corners at a curved angle.

You’ll find that this distortion is desirable in some situations. It can make images feel surreal, and if you stick an ultra-wide camera in your pet’s face, the results are very funny. But generally speaking, this distortion discourages people from using their ultra-wide camera when photographing subjects at a short distance.

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Other Cameras: Macro and Monochrome

Andrew Heinzman / Review Geek

Manufacturers tend to go a little crazy with the cameras in mid-range phones. They throw everything at the wall, usually in an attempt to make their inexpensive devices feel a bit more “premium.” For this reason, your phone may have a macro camera or a monochrome sensor.

A macro camera is specially designed to focus on small subjects, usually at an extremely short distance. You may use a macro camera to take detailed pictures of LEGOs, for example, though they’re typically used on flowers, insects, eyeballs, and other things that look dramatic when seen in great detail.

But unless you’re a fan of macro photography, a macro lens isn’t very useful in a smartphone. That’s why the latest iPhone uses a telephoto lens for its “macro shooting mode.” The results are fairly impressive, and we expect other smartphones to follow Apple’s lead in this area.

As for monochrome sensors—well, let’s explain a typical camera sensor first. When capturing full-color images, a digital camera sensor needs to individually capture red, blue, and green wavelengths, which are combined by an image sensor processor (ISP). Monochrome cameras capture all of this light in one quick go, providing a dramatic increase in contrast and eliminating the need for an ISP.

Of course, monochrome sensors only take pictures in black and white. You can use a monochrome sensor as a basic B&W camera, but generally speaking, smartphones include this sensor to increase the contrast of full-color images. Photos are simultaneously shot by both the main camera and monochrome sensor, and contrast information is pulled from the B&W image to enhance your full-color photo.

Again, these cameras are usually included in mid-range phones. As a result, there aren’t too many phones with high-quality macro cameras or monochrome sensors.

Time-of-Flight (ToF) Sensors: Improved Sense of Depth

The OnePlus 8T and iPhone 12 Pro both feature a prominent ToF sensor. Peter Cao / Review Geek

Some devices, including modern iPhones, use a time-of-flight (ToF) sensor to measure depth. It shoots out a burst of IR light, measures the amount of time that it takes for the light to return, and spits out a 3D depth map that can be utilized by computational photography software or “room mapping” apps.

The iPhone’s ToF sensor is accompanied by a LiDAR sensor. Both technologies perform the same basic task, though LiDAR sensors are a bit more accurate, as they send out multiple bursts of non-visible light. As you can imagine, the ToF sensor requires a lot less processing power, so it’s the ideal option for photography.

That said, a smartphone can take great photos without a ToF sensor. The iPhone primarily uses its ToF sensor to improve low-light focus and provide greater accuracy in Portrait mode. Rival smartphone brands have mostly avoided this technology, and Samsung abandoned ToF sensors after the Galaxy S9.

We should also note that the iPhone uses ToF and LiDAR for Face ID (and Samsung used to use this tech for its Iris Scan feature). That’s why facial recognition is more secure on iPhone than it is on Android—devices like the Pixel 7 scan 2D photos for Face Unlock, but the iPhone deals with 3D depth maps.

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