One 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

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.

I can't make this graphic appear at actual size on every phone, tablet and computer, but if you remember film, a full-frame sensor is roughly the same size as a single frame of 35mm film. If you don't, an APS-C sensor is just under an inch wide and a little over an inch diagonally.

Remember, these are the physical sizes of the image sensors. The resolution, aka how many pixels they have, is separate. You can have a 50-megapixel 1/1.28-inch sensor and a 24-megapixel full-frame, and vice versa. The resolution determines the size of the pixels for each sensor, which, in theory, will mean more light absorbed for a lower resolution sensor of a given size. As in, with two sensors of the same size, the one with the lower resolution will typically have larger pixels, which might mean it's capable of absorbing more light, but the sensitivity of the specific sensor and other factors mean this isn't 100% directly comparable with numbers.

Where do these sizes come from? It's a holdover from the days of analog TV and refers to the diameter of a theoretical vacuum tube with has light-gathering electronics roughly the same size as a modern sensor. I'm not kidding. Technically, the more accurate term is"1-inch type sensor," but that's usually shortened to "1-inch sensor" because it's easier to read.

The tech: Bin those pixels and stack those images

So yes, broadly speaking, a larger image sensor will capture more light than a smaller one. This can mean the camera with the larger sensor is better in lower light, able to create an image with less noise and less image processing, along with many other subjective and objective benefits. However, in many situations, the differences will be far less than their relative sizes imply. 

Let's start with an easy one to understand. All major phones now have an HDR photo mode, often turned on by default. This is different from the HDR on your TV. With photos, this means the camera is taking multiple images and combining them. In the simplest case, it captures a slightly underexposed image (too dark), a correctly exposed image and an overexposed (too bright) image. The phone will then combine these images so the final result will have more detail in the shadows and more detail in the highlights than a single image with the same image sensor could have managed. While this doesn't always work with perfect results, when it does work, it lets the camera punch above its weight, so to speak. 

This same technique, more or less, is used in the night, night sight or astrophotography modes found in most high-end phones. The phone takes multiple images, then aligns them and does some heavy computational photography that decreases noise and increases brightness by comparing all the images. This lets the camera's tiny sensor capture far more light than it could with a single exposure -- or at least with a single exposure short enough to avoid noticeable blur from camera shake.

Pixel binning is another technology. This is where groups of pixels are treated as one pixel. This effectively makes each pixel "bigger" and able to capture more light. Using this technique results in a photo with lower resolution than the sensor is technically capable of, but the image quality can be better. Detail isn't everything, especially when the trade-off is better dynamic range and usually less noise.  

Next, there's the lens. A "faster" lens lets in more light than a "slower" lens. While the difference isn't usually massive on phones, you might be surprised how a numerically small difference can be noticeable. With a faster lens, aka a bright lens, even just half a stop, can let in significantly more light, potentially offsetting some or all of the potential negatives of a smaller sensor. There are near-infinite camera and lens combinations, so the specifics matter. It's something else to keep in mind when comparing specs. 

Lastly, there's the sensor tech itself. Two sensors of identical size could perform radically differently depending on their design and tech. A full-frame sensor from 15 years ago might have worse dynamic range than an APS-C sensor that was released this year. There are a lot of variables. Often, but not always, full-frame sensors are in higher-end, mainstream cameras and typically feature the newest in sensor tech/performance.

When it might not matter

As a photographer, I can definitely notice the difference between a photo captured on a phone and one taken with a standalone camera with a big image sensor. Typically, the image has less noise, more genuine detail, more natural bokeh and better overall image quality. What's less obvious are photos taken with image sensors of similar but marketable size differences. I've owned a full-frame camera for years and love it, but over the past year, nearly every photo I've taken that I truly love has been shot with a camera featuring a smaller APS-C sensor. I don't think any of those images would have been improved -- or even looked noticeably different -- had they been taken with a full-frame camera.

To answer the question posed in the title: Yes, camera sensor sizes matter. However, the camera and the photographer matter more. If you're not into photography, the difference in the final result isn't going to be massive, especially considering the advanced features found in many devices with smaller image sensors. A camera or phone with a 1/1.9-inch sensor and one with a 1/1.28-inch sensor will differ in too many other ways to determine which will take better photos based on sensor size alone. For years, for example, Google Pixel phones used smaller image sensors than comparable Samsung and Apple devices but produced better low-light images thanks to superior computational photography.

If the camera doesn't have those features, such as the Panasonic Lumix ZS99, the biggest difference will be poor low-light performance. However, that camera's impressive optical zoom still makes it an appealing camera for many situations. So, as with anything, check reviews and nonmarketing image samples to see how the camera performs. 

For the most part, if you're just posting images to social media and you're not looking to take the ultimate shot when it comes to image quality, the size of the image sensor won't make a ton of difference.

If you're into photography -- or looking to get into it -- there are a lot of factors to consider when choosing the best camera for you. The adage that "the best camera is the one you have with you" holds as true as ever. As I mentioned earlier, I've transitioned back to an APS-C camera after years of shooting with a full-frame model. The smaller sensor is better suited to my needs in many ways, and the camera itself is lighter, more compact and easier to travel with. Would I step up to a medium-format camera if given the chance? Given the cost and size of those systems, probably not. For the way I travel, one would be more burden than benefit. I haven't sold my full-frame camera, though, and when I'm home, it's still more than capable of handling my professional work.

My advice, and I'm assuming you're fairly new to photography if you've read this far, is to get a camera you can easily afford, along with a couple of good lenses and get to know them inside and out. Once you've gained some skills, you'll probably have a better idea of what a more expensive camera with a larger sensor can do for you. Maybe you want a wider field of view than you can get with a smaller sensor, or lower-noise low-light images. Or maybe you want the narrowest depth of field possible so you can miss 90% of your shots because they're out of focus (been there). At that point, you can see what's shiny and new. Or even better, what you can find used at a discount.

About the author: In addition to covering audio and display tech, Geoff does photo tours of cool museums and locations around the world, including nuclear submarines, aircraft carriers, medieval castles, epic 10,000-mile road trips and more.

Also, check out Budget Travel for Dummies, his travel book, and his bestselling sci-fi novel about city-size submarines. You can follow him on Instagram and YouTube.