Why 108-megapixel cameras shoot at 12 megapixels: what gives more megapixels

In recent years, the resolution of smartphone cameras has steadily increased. First, 48-megapixel sensors were born, then came the turn of sensors with a resolution of 64-megapixels, and now no one is surprised by the use of monstrous 108-megapixel cameras in a smartphone. But if earlier an increase in camera resolution was directly linked to an increase in the detail of images, then the current generation of 108-megapixel sensors has a completely different goal.

How pixel size affects photo quality

Each camera sensor is made up of tiny pixels that capture light, measured in microns. For example, the recently released Xiaomi 11T smartphone in Russia uses a 108-megapixel Samsung Isocell HM2 sensor with 0.7-micron pixels, while the Samsung Galaxy S21 FE uses a 12-megapixel sensor with 1.8-micron pixels.

If you approach the issue superficially, it is easy to imagine that the more pixels in the camera sensor, the more detailed the images should be. But the size of any sensor, and especially the sensor of such a compact gadget as a smartphone, is extremely limited. But what happens if you place a different number of pixels on the same area? The more pixels there are, the smaller their size will be, which, by the way, is clearly seen in the example above.

And here comes the banal physics. Imagine two windows with an area of ​​0.5 and 1.5 square meters. m. Which one will bring more light into the room? Of course, larger. It’s the same with pixels: the larger its size, the more light it can capture. You’re unlikely to feel much of a difference in ideal shooting conditions, but on a cloudy day, twilight, or even more so at night, sensors with larger pixels will simply give a huge gain in image quality.

Pixel binning

So why, then, are manufacturers so diligent in increasing the number of pixels in their smartphone cameras at the expense of their size? The thing is that modern camera sensors support pixel binning technology, or, to put it simply, combining neighboring pixels into one large “superpixel”.

For example, the already mentioned Xiaomi 11T uses a 108-megapixel Samsung Isocell HM2 sensor with pixels whose physical dimensions are limited to a modest 0.7-micron. If everything remained as it is, the light sensitivity of such a sensor would be minimal, i.e. he could only take good pictures in ideal conditions.

However, thanks to the 9-in-1 pixel binning technology, the smartphone is able to combine nine adjacent pixels, due to which the effective pixel area increases to 2.1 microns, which, by the way, is even more than the Samsung Galaxy S21 FE with its “stock” 1 .8 µm pixels. Accordingly, its light sensitivity also increases, and with it noise decreases and the quality of shooting in low light increases.

The principle of operation of the technology is as simple as possible. Each pixel of the sensor captures only light and its intensity without any color casts. Well, to obtain full-fledged photographs, the sensors use color filters that transmit only light from a certain part of the spectrum (color) to a single pixel. So, some pixels perceive only red color, others – green, and still others – blue.

But this is what concerns the usual matrix. If we talk about pixel binning technology, then it involves the use of one filter not for an individual pixel, but for their group, which allows them to work as a whole. Moreover, the number of pixels in such a group can be different. In our example, one filter “covers” 9 pixels with itself – this technology is called 9-in-1, but, for example, 4-in-1 technology is usually used in 48-megapixel cameras, combining four neighboring pixels. In this case, in both cases, the resolution of the resulting photos will be the same – 12 megapixels.

However, manufacturers are well aware that pixel binning technology is not always needed, and sometimes the maximum detail of a photo is more important for users. Therefore, most smartphones with pixel binning technology have a maximum resolution shooting mode. It outperforms pixel binning when shooting on a bright, sunny day, but loses out in difficult lighting conditions without a chance.

conclusions

Increasing the resolution of the cameras of modern smartphones has made it possible to use the technology of pixel binning in them – the virtual combination of neighboring pixels into one large “superpixel”. Well, the increase in the pixel area, in turn, made it possible to improve its light sensitivity and improve the quality of shooting in low light conditions.

But, of course, a 108-megapixel camera will not always be better, for example, a 12-megapixel one. Indeed, in addition to the pixel size, the light sensitivity strongly depends on the quality of the optics, and on the size of the aperture, and on many other parameters. Nevertheless, pixel binning technology is considered to be an effective and relatively inexpensive way to improve image quality.

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