Why do we make double-triple-quadruple eyed cameras in smartphones instead of just improving the specs and keeping one lens?
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Multiple cameras allow using AI to assemble a better overall picture. For example if you overexpose one pic, and underexpose another a smart AI can puzzle a picture together that is perfectly lighted everywhere even though parts of the picture have vastly different lightlevels
The different lenses are for different purposes. You have a large ~~aperture~~ focal depth one for nice landscape pictures, you have a zoom one, you have a wide angle one for selfies and closeups or whatever. But given the very small amount of space available its extremely difficult to get good “does everything” results in a single lens and sensor stack. When you have a suitable all purpose or adjustable lens in a physical camera these can be several inches to several feet big, comprised of several dozen lenses inside that can move around; but even these are either very big and expensive, or are just good at one thing (telephoto zoom for example).
So its much easier (and thus cheaper) to put 3 sensors and 3 lenses in the camera, especially since real estate isn’t an issue anymore now that screens have to be like 10 or 11 inches.
edit: Aperture, focal length, whatever. I did mobile electronics but I wasn’t the optics guy.
It completely depends on the specific phone because there are many reasons a manufacturer my choose to do this.
One of the most common reasons is to have on camera that is either zoomed in farther or zoomed out farther to give the user the ability to change the amount of stuff in the picture without significantly lowering the quality.
On full sized cameras what is called optical zoom can be used, or an adjustable zoom through one lens, but this requires magnitudes more thickness than a smartphone can have.
When you make a lens, you have to give up something. That is, if you want a zoom lens, they generally are not as sharp, and don’t deal as well in low light as a prime (fixed) lens. They are also usually more bulky/longer/more heavy than prime. Fixed lens are sharper, and better in low light, but you give up flexibility with optical zoom. They also generally need less “glass” and have few or no moving parts. In many ways, good things for a very small space like a phone. Most phone makers have started using multiple camera lenses that (for the most part) are fixed, or nearly fixed prime lenses. You have an ultra wide, wide, and telephoto, for example. Often when you “zoom” on your phone, it is just changing between the lenses. Some have a little optical zoom. Some will also do a digital zoom for a bit before changing lenses, but in general the different lenses offer good low light, and different “zoom” levels.
Frequently they have different lenses for different purposes. Mine has one fixed focus for general use, one wide angle and one telephoto which it switches between depending on what settings/commands I use in the camera app. You can’t stack all of that functionality on one sensor/lens combo in the available depth, nor can you readily swap out lenses like on a dedicated, professional digital camera. So they just build in all three use cases because they’re pretty small and pretty cheap when they’re specialized like that.
Luckbot mostly covered it, but there’s another reason.
Think about a DSLR camera: If you want to take pictures at a certain distance, you would get a lens with a focal point that matches that distance. There’s [macro lenses which are for close up shots](https://www.lomography.com/lenses/4987-canon-ef-100mm-f2-8-macro/photos), [telescopic zoom lenses for distance](https://www.lomography.com/lenses/9524-canon-ef-70-300mm-f-4-5-6l-is-usm/photos?page=2), [wide angle lenses for landscape photography](https://www.lomography.com/lenses/277-canon-ef-s-18-55mm/photos), etc. Switching between them is simply a matter of swapping out your lens for another one.
Phone cameras are different for two reasons: One, they’re teeny tiny, so swapping out a lens on a camera the size of your fingernail really isn’t a compelling option. Second, digital camera modules are fairly cheap (at least from an OEM perspective). This means that it’s better to just put six of the same camera module, each fitted with a different lens and make your phone switch between them in software depending on what kind of picture you want to take.
The light collected by a camera is information about the world. Think of it as polling people’s opinions.
A giant lens and camera used for nature or sports photography can take in a whole city’s population worth of information at once. This allows for more accurate breakdowns of opinions and allows you to hear the thoughts of smaller, marginalized groups.
A cell phone camera lens can’t collect as much information no matter the quality of the lens because not as much light goes into it. It can be made to sample households in a neighborhood but not else.
One option is to add more cameras to sample more neighborhoods. Another option is for it to sample each person in a set of houses finely like a large lens (telescope lens). Another way is to sample sparsely over a larger region (fisheye or wide angle lens). Add all 3 types and you have more options in how to sample the world’s light information.
Adding to what others have said, multiple lenses can work together to provide clearer or more enhanced images. Most animals have more than one eye, which allows for stereoscopic (3D) vision. Cameras with multiple lenses can achieve this and other effects by combining their perspective and the data specific to each lens’ function to create a better image.
While most of the posters are explaining how the lenses work and why it’s cheaper to add more, the real reason is because it has the appearance of a new feature and differentiates from older models which causes people to buy new phones despite not needing one because they need to appear cool.
If the newer model looks the same as the old one nobody will buy it (well, a very small percentage of people who need a new phone will) because it doesn’t look different and won’t allow them to look cool.
They have different lenses. Often times it’s for optical zoom, and to achieve the same effect, the lens would need to move far more than it currently does, which means it must be much longer, and therefore stick out of the phone. This is also the reason that regular, non smartphone cameras have different lens attachments that the photographer can change between.
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