Advantages of 108 MP Camera Sensors and How the Pixel Binning Works


The number of megapixels is again a feature used by manufacturers to promote their new phones. Having more does not necessarily imply better image quality and, in recent years, it seemed that the number of megapixels had stopped growing excessively. Smartphones such as the iPhone or the Pixel are examples that with 12 megapixels it is possible to take incredible photos.



However, in 2019 we are seeing that many brands are betting on notoriously raising the number of megapixels. From the 16 megapixels, we go to 24MP, to 32MP, we have recently seen the first mobiles with a main 64-megapixel sensor, such as the Realme X2 Pro and soon we will have with us a device with 108 megapixels, specifically Xiaomi.

How did we get here? How have mobile sensors evolved in recent years? Here we explain the latest news of the Sony Exmor and Samsung ISOCELL, two major brands that dominate mobile photography and whose sensors are used by virtually all brands in their flagship phones.



How the 'Pixel Binning' works, the technique that is raising the number of megapixels to 108MP


The obvious advantage of having more megapixels is that the resulting photos will be larger and therefore we can enlarge more. Of course, a larger sensor also generates heavier images. This causes that the images of the mobiles have gone from occupying about 3-4 MB to be able to weigh more than 15MB in some of the new smartphones.

There are already many mobiles that add a 48-megapixel sensor. But to these, we must add the 64MP that we have seen in some models such as the Samsung Galaxy A70S and the 108 MP that the Xiaomi Mi Mix Alpha brings.

We speak of a resolution of 12,032 x 9,024 pixels, which gives us large images. We have not yet been able to check the weight of these images at full resolution, but if with 64MB we move around 15MB, with this 108MP it would not be far fetched to approach 20MB.

What is the point of adding such a large sensor? Why do we need so many megapixels if we then publish the photos on social networks where they are compressed? The answer is found in the technique of 'Pixel Binning', the mechanism used by these sensors to give real utility to the larger sensor size.




By combining adjacent pixels, the 'Pixel Binning' technique allows you to increase the sensitivity of the shot, virtually convert small pixels into larger pixels and capture more light and detail.

The key to these sensors of so many megapixels is that the resulting images are not always made to such a large size. What happens for example with 48-megapixel sensors, is that they take pictures in 12 megapixels. While those of 64MP, they do them in 16MP. Why? Because they combine 4 pixels in one. With the Tetracell technology of the 108-megapixel sensor, Samsung's name for the 'Pixel Binning', images are made by default at 27 megapixels.

Large sensors rely on improved photoelectric conversion and light collection techniques to "merge" adjacent pixels into one. In this case, the individual pixels are not as large as those of the smaller sensors, but when combined it does allow to have pixels of good size with the addition that can capture more information. And without increasing both the size of the photo and what happens when we shoot at normal size.

One of the techniques is the Quad Bayer color filter used by Sony in its Exmor sensors. At the moment, the Japanese company has not presented sensors of up to 108 megapixels, but it's current and extended 48MP sensor does use it. The technique consists of combining two adjacent RGB pixels that have the same color to increase the sensitivity of the shot. Each of the pixels is 0.8 micrometers, but when merged, pixels equivalent to 1.6 micrometers are achieved. With this combination, you get more light in night scenes and up to four times more dynamic range.


Sony and Samsung, the two largest manufacturers of mobile photographic sensors




The 108MP module of the Mi Mix Alpha is 389% larger than the 48MP module, according to Xiaomi data.

Xiaomi is the manufacturer that is leading the escalation in the number of megapixels, but it is not they who manufacture the photographic sensor that allows it. In this case, it is Samsung, through its ISOCELL sensors, who is pushing this race.

Samsung was the first with a 64-megapixel sensor, the ISOCELL GW1 and has recently surprised us again with the ISOCELL Bright HMX 108 megapixels, the first to overcome the hundred-megapixel barrier. We are facing a 38% larger sensor than the 48-megapixel sensor and with a size of 1 / 1.33", a record size that promises to absorb more light in low light conditions than its competitors.


With a size of 1/1.33 inches, this new ISOCELL HMX of 108 megapixels is larger than the large 1/1.54 "sensor that incorporates the Huawei Mate 30 Pro. In the case of the Chinese manufacturer, they bet on their SuperSensing sensors but Sony would be the provider.

Here we leave you with a small comparative table where we can see how mobile photography sensors have evolved in recent years. As we can see, the large sensors that greatly increase their amount of megapixels also have a smaller pixel size. On the other hand, mobiles such as the iPhone or Pixel with its 12-megapixel sensor, bet on directly larger pixels of 1.4 micrometers.

On the opposite side is Samsung with its 108 megapixels or the interesting proposal of the ISOCELL Slim GH1, a 43.7 MP sensor, very small and has the smallest pixels. A solution with a different approach, because in that case what is important is to be able to build a tiny sensor that does not help increase the size of the device.



MEGA PIXELS

SENSOR SIZE

PIXELS

MATE 30 PRO

40MP
1 / 1.7 "
1.0 µm

MATE 30 PRO (WIDE ANGLE)

40MP
1 / 1.54 "
1.0 µm

GOOGLE PIXEL 4 XL

12MP
1 / 2.55 "
1.4 µm

IPHONE 11 PRO

12MP
1 / 2.55 "
1.4 µm

EXMOR IMX586

48 MP
1 / 2.25 "
0.8 μm

ISOCELL S5KGM2

48 MP
1 / 2.25 "
0.8 μm

ISOCELL SLIM GH1

43.7 MP
1 / 2.65 "
0.7 μm

ISOCELL S5KGW1

64 MP
1 / 1.72 "
0.8 μm


Huawei with the four sensors of the Mate 30 has done an exceptional job, leading in sections as different as the size of the sensor or the number of megapixels. But the battle centers between Sony and Samsung. The 108 megapixels come from the hand of Samsung, but it was Sony with its 48-megapixel IMX586 the manufacturer that has collaborated most in expanding the technique of 'Pixel Binning' and ultimately to democratize access to mobiles with a large number of megapixels.



Xiaomi, the manufacturer that seeks to release the 108 megapixels

Through a message on the Chinese social network Weibo, Xiaomi has anticipated that next November 5 will present the new CC9 Pro mobile, with which they intend to "create the most powerful image system in the history of Xiaomi". Beyond the aspirations, what we can see in the promotional image is a five-camera system, with 5x optical zoom and the main sensor of 108 megapixels.



Although in reality, it would not be the first time that Xiaomi presents a mobile with 108 megapixels since the Mi Mix Alpha will also incorporate the Samsung ISOCELL HMX sensor with this size. We will have to wait for their official presentation and be able to test these devices for a while to discern to what extent it is worth incorporating such a large amount of pixels. A strategy that theoretically comes to improve the dynamic range and the obtaining of light, but where in practice we have seen a very slight improvement.




The sensor size will continue to grow


Other factors are involved in the camera of a mobile phone in addition to the sensor used. We have for example the software level processor or the lens applied. This is why not all phones with the same sensor make the same type of photos. Although, the sensor indeed is one of the main components and on which the experience revolves.

The 108 megapixels may seem an extraordinary figure, especially considering that authentic referents such as the Pixel or iPhone only offer 12 megapixels. Do you mean that these phones with 108 MP will be nine times better? Now here near. And it is a difference that will go more and more, because, in the same way that the number has doubled to 108MP, we will soon see cameras with 192 megapixels, according to Qualcomm.

What would such a camera look like? Details are still unknown, but it's hard to imagine that in the same way that the 108 MP camera takes photos in 27 megapixels, the 192 megapixel camera can take photos in 48 megapixels with a 4-in-1 'Pixel binning' or even make them in 12 megapixels in case a more advanced technique appears to combine a larger number of pixels into one.

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