We explain
The size of the sensor is more important to how good the camera is than the number of megapixels.
The number of megapixels in the mobile camera has become the standard measure of how good a mobile camera is. It has been around since the days when cameras were often low-resolution. The first iPhone, for example, had a 2-megapixel camera and then a 4-megapixel camera was obviously better because you got smaller pixelated images.
Today, on the other hand, the resolution is usually not a limitation, and above all it is not a good measure of how well a mobile camera takes pictures. A much better measure is the sensor size.
The sensor size is usually given as a fraction of the type 1/x inch, ie how big a part of an inch the sensor is. The smaller the second number, the larger the sensor is. As an example, the iPhone 17 has a 1/1.56-inch sensor for the main camera, which is about two-thirds of an inch. The wide-angle camera’s sensor, on the other hand, is 1/2.55 inch, that is, just a little more than half as big. This explains why the images from the wide-angle camera are worse even though the cameras have the same resolution.
In practice, sensor size isn’t an exact measurement, as you’re measuring the physical dimensions of the sensor and the actual area used by pixels is smaller and can vary between manufacturers, but it’s close enough for comparisons.
In practical terms, this means that the larger the sensor you have, the larger the pixels will be. They can then take in more light, and indicate their color value with greater accuracy and with less risk of error. That difference is most noticeable when shooting in the dark, where the amount of light reaching the camera is small. Then every extra registered photo can make a difference.
If we look at the Samsung Galaxy S25 Ultra and the iPhone 17 Pro, the Galaxy S25 Ultra has a 200-megapixel sensor in the main camera, while the iPhone 17 Pro has a 48-megapixel one. But the sensors are roughly the same size, 1/1.3 in the Galaxy S25 Ultra, 1/1.28 in the iPhone 17 Pro. The individual pixels in Samsung’s camera sensor are thus much smaller.
In theory, it is a disadvantage to have many but small pixels on the camera sensor compared to fewer but larger ones, given the same size of the sensor. This is due to several reasons, for example, the pixels do not take up the entire surface of the sensor and therefore there is more dead space, or the light, due to its wave-like nature, spreads when it passes something as small as a mobile camera lens, and this spread tends to be larger than the pixel if you have 200 megapixels on a mobile camera sensor. This means that the noise increases in the pixels if they are too small.
That it is still not obvious which is the best of fewer or more pixels becomes clear from the fact that the two major manufacturers of mobile camera sensors, Sony and Samsung, each chose their own track. Sony generally prefers sensors with 50 megapixels, while Samsung’s best sensors often have 200 megapixels. In Samsung’s case, various technical solutions are highlighted that compensate for the problems that arise with pixels that are too small.
To summarize, the size of the sensor is one of its most important characteristics, but it may also be worth keeping an eye on the size of the individual pixels.
This is an excerpt from a longer article where we explain how mobile cameras work, which was previously published exclusively for Plus members on Mobil.se. Here you can become a Plus member and thus get direct access to all articles on Mobil.se. As a plus member, you get collected tips and many other in-depth, guiding articles. You can find the entire original article here.