Why Do Smartphones Have Multiple Cameras?

Ever since the camera became one of the biggest selling points of smartphones, manufacturers have been putting a lot of effort into improving their performance.

It wasn’t until 2011 that a new trend emerged－phones multiple rear cameras. This saw the introduction and rise of dual-camera smartphones. Several years later, mobile phones with three or more rear cameras entered the market and have since become the norm.

However, this might raise a few questions for those that don’t fully understand how smartphone cameras work. Why do smartphones have so many cameras? What does each camera do? Does a smartphone with more cameras take better pictures? Let’s take a look.

Note: For this article to make more sense to you, I suggest you read up on focal length before you continue if you’re not already familiar with it.

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Why do phones have more than one camera?

The main reason why some phones have many cameras is to improve the photographic capabilities of the smartphone. Typically, each camera has a different angle-of-view, which means one camera can fit more things in the shot (wide-angle) than another (telephoto).

Some phones have a monochrome sensor for increased light sensitivity, while others offer depth information. Data from the different cameras can be combined into a clear photo with seemingly shallow depth-of-field and good low light capability.

The presence of multiple cameras with different focal lengths is what makes it possible for smartphone cameras to achieve their version of optical zoom. By switching between a camera with a wide angle-of-view and one with a narrow angle-of-view, the camera is able to zoom in and out without experiencing as much picture quality loss as you would when using digital zoom.

Thanks to computational photography, data from all the cameras at the back of the phone can be combined in order to produce the best quality photos possible on that phone.

But, here’s the question…

Why don’t smartphones have one camera that can do everything?

Some smartphone manufacturers tried that in the past but it didn’t catch on because of size. Nobody likes a big phone. For one smartphone camera to be able to zoom optically, it would require a zoom lens. And as evidenced in the past, not enough people liked having a phone with a protruding lens at the back for it to become a thing.

In order to fully understand why a smartphone would need more than one camera, you need to understand focal length and its impact on the lens’s angle of view (sometimes called field of view).

Simply put, focal length refers to the distance between the centre of the lens and where light converges on the sensor. This distance is measured in millimeters, e.g. 50mm. Lenses with short focal lengths such as 24mm capture more of a scene and are therefore said to have a wide angle of view. The longer the focal length, e.g. 130mm, the narrower the angle of view and therefore the more magnified or zoomed-in the image to a particular area.

In traditional photography, a variable focal length lens is one that changes its focal length as it zooms in or out between a wide shot and a closeup. The 18-55mm kit lens is a typical example of such a lens. What those numbers mean is that this lens can shoot as wide as a 18mm lens but when zooming in, the glass elements inside the lens barrel move and narrow the shot to the focal length of a 55mm lens. When the lens elements move, the focal length changes.

A fixed focal length lens has no movable glass elements in the lens barrel. This means that you cannot zoom in or out using this lens as it only has one fixed angle of view.

This fixed focal length approach is how smartphone manufacturers keep their devices thin. I guess it makes more sense to them to have multiple cameras with different focal lengths to function independently yet in conjunction with each other through software than to have everything all packed into one large, unsightly camera bump.

To keep their devices thin, smartphone manufacturers have opted to add more cameras to their phones. Each camera has its own type of lens with its own fixed focal length.

Another reason why phones have multiple cameras is to improve the quality of the photos they produce, particularly in low-light conditions. Big cameras such as DSLRs don’t have the same low-light issues smartphones have because they have large sensors with large pixels.

Unfortunately, smartphones have the smallest sensors of any consumer camera because of size limitations. To combat this, data from multiple sensors can be combined to build a better image than what can be captured by one image sensor.

This approach is similar to how some space telescopes are able to photograph clear and bright images of deep space.

What does each camera on a mobile phone do?

Primary camera

Camera design differs from manufacturer to manufacturer but the main camera on most smartphones has a wide-angle lens with a short focal length that gives it a wider angle of view.

It is perfect for shooting things like landscapes, street photography or a large group of people without stepping too far back. Wide-angle lenses allow a lot of light in and have a deep depth-of-field which means everything in your shot remains in focus.

Ultrawide-angle camera

This lens goes even further than a standard wide-angle lens which means you can capture even more of a scene because it has a much shorter focal length and therefore a much wider angle of view. With this lens, it possible to stand at the bottom of a tall building and fit the entire structure in your shot.

Telephoto camera

Unlike the wide-angle lens, the telephoto lens has a much longer focal length which means that instead of getting a shot that captures the entire scene, you can zoom into one particular area. Some smartphones use software to match the data from the other cameras to create a smooth zoom effect as the camera unit switches between the wide lens and the telephoto lens.

Monochrome sensor

A monochrome (black and white) sensor has no colour filter array which means it can capture sharper images than a colour sensor. It also means that the monochrome sensor is more sensitive to light which is good for low light situations. Pictures taken in true black and white (not processed through a filter) are known to be sharp and full of contrast.

Smartphones that have this camera, use the sharpness and contrast information from it and blend it with the image from the colour sensor to create a final colour image with better lighting and sharpness.

And if you’re a fan of black and white photography, it is possible on some smartphones to isolate the monochrome camera and take photos in true black and white.

Time-of-Flight camera (Depth sensor)

A Time-of-Flight (ToF) camera is basically a depth sensor. It shoots out an infrared light and measures how long it takes for the light to reach the subject and bounce back to the sensor. This data is used to create a depth map of the subject and the surroundings.

It is the information from the depth sensor that is used by software to separate the foreground and background and thus create the blurry background bokeh effect.

Not all smartphones have a dedicated ToF camera. Some manufacturers have opted to rather use information from the other cameras in order to figure out the depth in the scene through complex algorithms.

Camera array setup

Different manufacturers have their own choices of how many cameras they will put on their smartphone. Not only that, but they also decide which combination of lenses and sensors they want to install.

Dual Camera

The dual camera setup has been around for a long time but didn’t really pickup until around 2016. These days, however, the dual camera setup is mostly found on cheap phones.

Dual camera smartphones come in a variety of combinations:

Triple camera

This combination builds on the dual camera setup and opens up a whole lot more possibilities, depending on the types of cameras that make up the rear camera array.

The most common triple camera setup consists of a wide-angle camera together with a telephoto camera and an ultra-wide-angle camera. However, other combinations of cameras exist. It all depends on what the manufacturer wants to include in their camera.

But almost all smartphones with three cameras have a wide-angle lens and a telephoto lens.

Quad camera and more

And just when you think three cameras is enough, quad camera smartphones come into the picture. At this point, phone manufacturers can add even more novelty to their cameras. For example, the macro camera is mostly found on phones with four cameras. However, this is not the given standard.

The Nokia 9 PureView is famous for its five camera array. But only two of the five cameras had colour sensors. The other three cameras had monochrome sensors. This is uniquely different to how other smartphone manufacturers set up their multiple cameras.

Nokia 9 PureView with 5 cameras and depth sensor

Conclusion

The question of whether smartphones really need more than one camera is truly a subjective matter. Sure, single camera smartphones have been taking fairly decent photos for what they are but there’s no denying the difference that two or more cameras can make. That being said, a picture taken by a single superior camera can look better than that of multiple mediocre cameras.

If you’re like me and you buy a smartphone mostly based on the camera, make sure you learn and understand all the specs. Know what you’re looking for in a smartphone camera and go for that. You might just find a dual camera phone that satisfies your needs better than a phone with more cameras that don’t do much.