GoKawiilOne of the headline specs of any camera -- whether it's a point-and-shoot, mirrorless model or even a smartphone camera -- is the size of the image sensor. It's clear in the marketing that a bigger image sensor is better, but why? Does a small increase in sensor size really make that much of a difference? Should you, when looking for a new camera or phone, consider sensor size?
The truth is, maybe. In certain situations, a larger image sensor can have significant advantages over a smaller sensor, but the specifics matter. Different lenses, technologies such as pixel binning and advanced computational image-processing techniques can all help smaller sensors perform more like larger ones. Also, depending on what kind of photos you're taking, it might not matter at all. Here's why.
The basics
Two camera modules like those found in modern phones. Wongsakorn Napaeng/Getty Images
An image sensor is a device that absorbs light and converts it into electrical signals that are then interpreted by the camera's (or phone's) processor to create an image. They're designed to absorb as much light as possible. Modern image sensors are pretty good at this, certainly relative to those found in cameras from the early days of digital photography.
At the risk of stating the obvious, there's plenty of light available during the day. Indoors or at night, not so much. Your eyes can easily adapt to those extremes, but small image sensors often struggle. With less surface area to capture light, they can produce images that are too dark -- assuming they capture a usable image at all.
A larger image sensor, all else being equal, has more surface area to capture light. To put it simply, imagine it's raining and you want to collect some water. If you go outside with a shot glass, you'll catch a little. If you go outside with a bucket, you'll catch much more. The same principle applies to image sensors, though the details are a bit -- OK, a lot -- more complex.
The sizes of sensors
The image sensors -- our rain buckets, if you will -- come in a variety of sizes. In product marketing, you'll often see terms like "1-inch," "APS-C" and "full-frame." They're descriptive without being especially clear. For example, a 1-inch sensor isn't actually 1 inch in any dimension, including its diagonal measurement.
This colorful illustration, skillfully crafted by yours truly, should give you a sense of the relative sizes of some of the most common image sensors.
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