Why do smartphones have triple-quadruple cameras when “dedicated” cameras have just one? What makes it better and why do we not see the 3-camera setup on actual cameras then?
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It all depends on what goals you have for a camera system. In many cases, 3 prime lenses can be smaller and lighter and have a faster aperture than 1 zoom lens covering the same range of focal lengths. Engineers have come up with all sorts of solutions to meet different needs.
[The DJI Mavic 3 Pro drone has 3 cameras](https://www.zdnet.com/article/the-worlds-first-drone-with-three-optical-cameras-just-launched-why-that-matters/) specifically to save space and weight versus one camera with a zoom lens.
In the past, motion picture film cameras often had rotating lens turrets with 3 lenses. Someone is designing a new one to use with modern digital cinema cameras. [Here’s a picture of an old German Arri film camera with a lens turret next to a new German Arri digital camera with a prototype lens turret.](https://www.cined.com/content/uploads/2023/04/VERTIGO_old.jpg)
For reference, [here’s the same Arri digital camera with a cinema zoom with third-party zoom motors and other accessories.](https://www.reddit.com/r/pics/comments/mvabwx/focus_puller_amanda_wojtaszek_with_an_arri_amira/)
The reason for the multiple cameras are more about the lenses than the cameras.
On a full size camera you can change the lens to match what you’re shooting at, which is harder on the phone, so instead they have started building in different types.
Each lens, in their miniature size, comes with different specializations/limitations. For example, you have one lens for Macro photography – stuff that you go very close up to, like an insect or a flower or drop of water. Then, one for photography, with high amount of pixels, specialized on taking still photos. Another one for videos, in full HD or 4k even, specialized in giving good quality with moving images and capturing them really fast (high framerate so the videos don’t stutter/flicker). And then one very tiny on the front, for selfies.
That’s a normal, lower-to middle-level smartphone setup. Some better smartphones come with more lenses, for more different occasions. Maybe multiple ones for photography, like, wide-angle for panorama, one for better sight at low lighting, etc.
There are even some with really ridiculous amounts of lenses, like 10 or even more. I’ve seen one today with 16 lenses, even named after it (L16). Maybe for 3D, stereoscopic, whatever. At some point they may even be able to look into the past or give you an MRT while brewing your coffee while you’re diving.
From [Little Brother](https://craphound.com/littlebrother/Cory_Doctorow_-_Little_Brother.txt) by Cory Doctorow
>I went into the bathroom and took off the toilet-paper roll and replaced it with a fresh one. Luckily, it was almost empty already. I unrolled the rest of the paper and dug through my parts box until I found a little plastic envelope full of ultra-bright white LEDs I’d scavenged out of a dead bike-lamp. I punched their leads through the cardboard tube carefully, using a pin to make the holes, then got out some wire and connected them all in series with little metal clips. I twisted the wires into the leads for a nine-volt battery and connected the battery. Now I had a tube ringed with ultra-bright, directional LEDs, and I could hold it up to my eye and look through it.
>I’d built one of these last year as a science fair project and had been thrown out of the fair once I showed that there were hidden cameras in half the classrooms at Chavez High. Pinhead video-cameras cost less than a good restaurant dinner these days, so they’re showing up everywhere. Sneaky store clerks put them in changing rooms or tanning salons and get pervy with the hidden footage they get from their customers — sometimes they just put it on the net. Knowing how to turn a toilet-paper roll and three bucks’ worth of parts into a camera-detector is just good sense.
>This is the simplest way to catch a spy-cam. They have tiny lenses, but they reflect light like the dickens. It works best in a dim room: stare through the tube and slowly scan all the walls and other places someone might have put a camera until you see the glint of a reflection. If the reflection stays still as you move around, that’s a lens.
>There wasn’t a camera in my room — not one I could detect, anyway. There might have been audio bugs, of course. Or better cameras. Or nothing at all. Can you blame me for feeling paranoid?
having multiple cameras on phones has a similar concept with having multiple lenses for real cameras.
On an actual camera you have the ability to physically move the lenses to zoom in and out with optics (you’re physically changing the distances between lenses and sensors). On a phone, you don’t have the space for this mechanism, so instead, they include multiple smaller cameras with fixed optical zooms.
I have a camera with a 50x optical zoom, you can see the camera physically extending to achieve that.
So, a camera works by taking the light reflected off something, focusing the light through specially curved glass (called a ‘lens’), and recording that light on something else. Sometimes it’s film, sometimes it’s a computer sensor that changes the light it sees into a digital picture you can look at on a computer later.
Phones cameras have small lenses, and less light can get in. To make up for that, some of the holes that let in the light are much bigger. Others are the normal size, or smaller.
When the hole in the lens gets bigger, more light gets in, but you can see less of the image behind the thing you’re trying to take a picture of. If the hole is smaller, you can see more of the stuff behind the thing you’re taking a picture of, but less light gets in.
If you have a special ‘telescoping’ type of lens, and you make the case of that lens get bigger, it can see things farther away, but the picture gets narrower. But doing that also makes less light able to get inside.
If you make the lens get smaller (wide angle or macro photography) it can only see things closer up, but it lets a lot more light in and can see a wider picture.
Phone camera lenses can only ‘telescope’ so much because they have to fit inside the phone. So to give you the option to see far away stuff *and* close up stuff *and* take normal photos, they have to put three lenses on it. A normal DSLR can do all that with one lens (in theory).
The smartphone having multiple cameras is really just a by-product of the smartphone wanting multiple lenses.
A dedicated camera has a single, larger, adjustable lens. There’s no room for a big adjustable lens in a smartphone, so instead they use small, non-adjustable lenses and therefore need multiple cameras to align with each independent lens.
The other part is that the long dimension of a lens is perpendicular to the plane of the screen, which is the most limiting dimension of a phone. There’s height and depth available, but really not much depth/thickness available. So it makes sense to halve multiple thin components rather than one deep/thick one.
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