The megapixel war between smartphone makers feels like a war that’s as old as time now. It all started with tiny VGA cameras, moving up the megapixel ladder to over 100MP cameras on phones today. And as long as that war has existed, experts have warned that the megapixels don’t matter when it comes to camera quality. It’s been proven before as well, with Apple’s 8MP iPhone cameras taking Android phones’ lunch money even though they had surpassed the iPhone in megapixel count. In 2021, phones like the OnePlus 9 Pro, Vivo X60 Pro+ and others are once again delivering the same lesson. Why? Sensor size.
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What is sensor size?
Nothing is more important for a camera (any camera) than the amount of light it can take. And it’s the sensor, a tiny semiconductor inside the camera that holds a bunch of photosites that collect light and convert it into electrical signals. Sensor size determines how many photosites can be placed on a sensor. As you may have gathered already, larger the sensor size, larger the number of photosites, and larger the light gathered by a camera. The implications of this are many.
For a camera, any scene you shoot is essentially millions of light rays bouncing off the various items and subjects in the scene. For a digital camera, this essentially means more data about the scene you’re shooting. More data means better pictures. Comprende? Let’s move on.
Wait! There’s more…
It doesn’t end there — the number of photosites also depend on resolution to an extent. At a given resolution, the size of each photosite will depend on the sensor size. Smaller sensors will have fewer photosites and larger sensors will have more. Similarly, if sensor size is kept constant, the size of photosites will become smaller with increasing resolution.
Photosites hold the pixels and pixels are what finally make your photos. So the photosites have to be packed closer to each other when resolution goes up at a fixed sensor size. When light falls on these closely packed photosites, it can leak from one pixel to another, causing noise in the final image. This is called sensor size and you will often notice this effect in your final images. Smartphone cameras today employ aggressive noise reduction algorithms, but having this issue at a hardware level can still be problematic.
This problem can be even worse now, since most camera sensors have four pixels per photosite instead of one. Oh by the way, these pixels are what determine the megapixel count, meaning it doesn’t matter how many pixels you cram on a sensor, you won’t get a good photo unless you can light them right.
So, now that you know what sensor size is…
But that’s all the technical stuff, the stuff you won’t even actually see when you’re shooting with a phone or any other digital camera. The sensor size can impact some very real settings that you tinker with on a smartphone’s camera — specifically the exposure settings and dynamic range.
Remember when we said the photosites gather more light in larger sensors? This directly impacts the dynamic range of the camera, that is, the gradation from light to dark. The more range a camera has, the better the final image will look. The human eye perceives the different shades of light almost involuntarily, but a camera needs data to interpret this. So, larger sensor size means more data and hence more dynamic range. Smaller the sensor size, lower the dynamic range, cram as many megapixels as you will.
Speaking of smaller sensors. To gather more light on a smaller sensor, photographers have to shoot at longer shutter speeds. But for most average users, holding the camera steady for ever a second or two is a pretty tough task. So, unless you’re shooting every photo on a fixed tripod, you’re probably going to get blurry images when shooting at higher exposure times. You will notice this most often when shooting low light photos, like say in a crowded bar, where every photo shows people moving around. A larger sensor will resolve the available light in low light situations at shorter shutter speeds, and hence produce sharper photos with better colours.
Is this why smartphone cameras can’t beat DSLRs?
You’re absolutely right. No matter how good they get, smartphone cameras cannot match the sensor size used in DSLRs, simply because a phone’s housing doesn’t have enough space to fit those sensors. This is why professional photographers will always choose a DSLR camera over a smartphone when it comes to critical work, and it’s also why DSLR cameras are more versatile than smartphones.
Companies have created many algorithms — often using machine learning technology — to offset these disadvantages, but some things just cannot be solved by software yet. Computational photography (photography using software) has advanced a lot, but all algorithms need data and the sensor will remain the provider of that data.