Everything you ever wanted to know about smartphone cameras, from resolution to aperture, and beyond (2024)

Mobile photography makes photography accessible to the public. Instead of needing to know the intricacies of all the buttons, dials, and settings on a dedicated camera, just open your camera app and take a photo. While taking a photo is straightforward, understanding a phone's camera specs may be complicated (what does μm mean, anyway?).

If you've wondered how camera phone makers describe their devices' cameras, you've come to the right place. This guide breaks down the common terms used to describe mobile camera hardware, literally and practically.

Resolution (MP)

A camera's resolution, measured in megapixels (MP), is the number of physical pixels (discreet units that collect light, also known as photosites) on the camera's sensor. One megapixel equals roughly one million pixels. Images from a 12-megapixel camera contain about 12 million individual pixels. When shooting at full resolution, a camera takes photos that contain the same number of pixels as there are on its image sensor. Think of resolution as shorthand for the photo size.

Pixel size (μm)

The physical pixels on a camera's image sensor are tiny. On modern smartphones, individual pixels are a fraction of the width of a single human hair. You'll see the pixel size noted in μm — the symbol for micrometers. One micrometer is one one-millionth of a meter. For example, the 50-megapixel primary camera sensor on the Google Pixel 7 has a pixel size of 1.2 μm.

Pixel size matters because the larger a camera's pixels, the more able it is to see in dimly lit conditions. Bigger pixels have more surface area to let light through. Many phone cameras compensate for their tiny pixel size through pixel binning, which uses software to digitally combine adjacent pixels into larger, more light-sensitive units by sacrificing resolution. The Samsung Galaxy S23, for example, has a 50-megapixel primary camera with 1μm pixels. However, by binning groups of four pixels, the phone can take photos at 12.5 megapixels with artificially large 2μm pixels, which boosts low-light performance.

Sensor size

In mobile photography, sensor size matters for the same reason pixel size matters. A larger sensor has a larger surface area that collects more light, improving performance in dim conditions. Bigger sensors can also accommodate more individual pixels without sacrificing light sensitivity. All else being equal, a one-inch 50-megapixel sensor performs better in low light than a smaller 1/1.2-inch 50-megapixel sensor.

Sensor sizes are often denoted by a fraction. For example, the primary camera on the OnePlus 11 has a 1/1.56-inch sensor. It looks odd, but it's only a fraction. A 1/1.56-inch sensor is about 0.64 inches across from corner to corner (1 ÷ 1.56 = 0.641).

Aperture (f/stop)

A camera's aperture is the opening that allows light to pass between the lens's glass and the image sensor. Aperture is measured in f-stops, denoted as a number following an f. For example, the primary camera on the Samsung Galaxy A54 has an f/1.8 aperture.

As with sensor size, the aperture's strange-looking notation is also a fraction. The numerator, f, is a variable that stands in for a given lens's focal length. Plugging that number into the fraction tells you the diameter of the aperture's diaphragm, the circular bit that sits around the opening (focal length isn't discussed much in mobile photography, so we won't dig too deep into it here).

Counterintuitively, the smaller the denominator, the larger the aperture's opening. All else being equal, a camera with an f/1.8 aperture takes brighter photos with a shallower field depth than a camera with an f/2.8 aperture.

Aperture affects light sensitivity (a larger opening collects more light, resulting in better low-light performance) and depth of field. The narrower a camera's aperture, the sharper parts of a photo that aren't in focus appear.

Field of view

A smartphone camera's field of view is the area the camera can see at any given time and is measured in degrees. In mobile photography, the field of view is often mentioned in the context of ultra-wide secondary cameras. For example, the Motorola ThinkPhone has an ultra-wide shooter with a 120° field of view. It all comes down to geometry. If you make a triangle by drawing a line between the two opposite ends of a camera's field of view, between each of those corners and the camera sensor, the angle of the corner at the sensor would be 120°.

The same photo taken on the Pixel 7's 114° ultra-wide vs. the 7 Pro's 125.8°.

A larger field of view number means more stuff is visible in the frame. The 125.8° ultrawide on the Pixel 7 Pro can see more at once than the ThinkPhone's 120°. Wider fields of view also mean objects closer to the camera can appear distorted.

Image stabilization (OIS, EIS)

Image stabilization is exactly what it sounds like. It's a technology that seeks to stabilize the images you take to minimize the impact of slight camera movement and prevent blur. There are two kinds of image stabilization: optical (OIS) and electronic (EIS).

In mobile photography, optical image stabilization works by mechanically shifting your camera's lens slightly to compensate for your phone's movement. You'll hear a faint clicking near the camera module when you shake a phone with OIS. That's the lens shifting.

Electronic image stabilization works by digitally cropping in on an image. You may notice this effect when you swap from your phone's photo mode to video recording. When the phone detects it has shifted in one direction, it compensates in the image by digitally shifting in the opposite direction.

For more, check out our guide to the different types of image stabilization in mobile photography.

Autofocus (Laser AF, PDAF)

You probably have a good idea of what autofocus is. However, different phones use different methods to dial in the focus automatically. Standard autofocus works by detecting contrast between adjacent pixels, operating on the principle that in-focus objects in the frame naturally exhibit higher contrast. Two other types of autofocus you'll likely see pop up frequently are laser autofocus and phase detection autofocus, or PDAF.

Laser autofocus works by emitting an invisible beam of light from an autofocus module, which bounces off whatever the camera is pointed at. The phone measures the time it takes to detect the laser's reflection and, with some quick math, works out roughly how far away the subject you're trying to photograph is, dialing in its focus to match.

PDAF is more complex. In smartphones, PDAF takes predetermined pairs of pixels and ensures they're exposed to the same amount of light. If the light falling on the two pixels in a given pair is uneven, the image isn't in focus over that particular pair. The degree of unevenness lets the phone know how to move its camera lens, forward or back, to achieve proper focus.

Most phones combine these techniques, ideally resulting in quick and accurate autofocus.

Have you caught the mobile photography bug?

We hope this guide demystifies some of the terminology phone manufacturers use to describe their camera technology. There's a lot of it. Only a good combination of all these factors can lead to a positive photo-taking experience. If you feel like delving deeper into mobile photography, we have handy guides on the Google Pixel camera app, plus some photo editing tips for beginners.