The image sensor of the Mi 12S Ultra is not “an inch” large, but it is normal

"This is the world's largest smartphone camera?"

This is the title of the teardown video of the Xiaomi Mi 12S Ultra by JerryRigEverything, a famous YouTube blogger.

Similar to the official promotion of the Xiaomi Mi 12S Ultra, whether it is JerryRigEverything or other similar bloggers, they will focus on the built-in 1-inch sensor.

After a routine operation, Jerry went straight to the point and carefully measured the true size of the so-called one-inch sensor with a vernier caliper.

The results surprised him.

This sensor is not "one inch" by any measure. It is about 0.54 inches (13.7mm) long, and the diagonal is only 0.66 inches (16.7mm). Is this a false mark of Xiaomi?

One inch fan

The imaging function of smartphones is becoming more and more important, and it has almost become the main battlefield for manufacturers.

Similar to the field of traditional cameras, the strength of a camera has a lot to do with the size of the sensor. Although now is the era of "computational photography", the advantages of low signal-to-noise ratio of large sensors are still irreplaceable.

From the early 1/3.6 inch to the current 1 inch, it is only a few years time, and the mobile imaging has achieved remarkable results.

▲ The dimensions of the sensor in the picture are wrong!

Just last year, the image sensor size of many products has touched the one-inch ceiling.

It's just for the one-inch publicity "gimmick" that the full-size one-inch product was not perfectly used for imaging, but only a part of the center was imaged, which caused a lot of discussion.

In the follow-up, when the Xiaomi Mi 12S Ultra also used "one inch" as the selling point of its images , approval and doubts also came.

Even if Sony endorses it, or starts from the picture size, there is still no intuitive disassembly. But Jerry's disassembly does not directly prove that "an inch" is really an inch.

Instead, the diagonal length of the sensor is only 66% of an inch.

This inch is not that inch

"One inch" is about 25.4mm when converted to metric units. In other fields, such as TVs and monitors, it mostly refers to the length of the diagonal of the screen.

According to this thinking inertia, an inch on the sensor should also refer to the diagonal length, as Jerry did in the video.

In fact, the name "one inch", or this size has no "restriction" relationship with the size of the sensor (CMOS), but is more like a historical issue.

Imaging has been developed for a long time. The early recording medium was some chemical photosensitive materials such as film. After entering the 21st century, a series of electronic devices such as electronic camera tubes, CCDs, and CMOS replaced film, and the working method of cameras has become what we are now. Familiar appearance.

In the film era, the film size was not as rich as the size of the current electronic sensor. At that time, 35mm (36mm x 24mm) film and Olympus half-frame machine (a film divided into two) were common.

With the transition to the electronic age, subdivision sizes first appeared in the 1950s in the days of camera tube imaging.

▲ The picture of the camera tube comes from: wiki

The so-called dimensions of 1/1.8 and 2/3 inches are actually the diameter of the glass casing of the camera tube.

Since the glass tube originally had a certain thickness, the actual circular imaging area was only 60-70%.

With the improvement of silicon technology, the appearance of CCD and CMOS square sensors has gradually replaced the camera tube.

▲ Comparison between the diameter of the camera tube and the square CMOS area. Picture from: dpreview

Even though there is no strict mathematical relationship between the area of ​​the square sensor (diagonal) and the diameter of the camera tube (about two-thirds), it may be due to convention or there is no better standard, and the final CMOS size is still used. 1/1.8, 2/3 inch in the age of camera tubes.

There is no defined mathematical relationship, and there is no so-called standard. Among the modern "one-inch" sensors, the real size of the square CMOS is also slightly different.

▲ Jerry put on a tube, just "one inch", and it all explained

As a representative of one inch, the Sony RX100 series black card camera has a sensor size of 13.2mm x 8.8mm, a diagonal length of 15.86mm, and an area of ​​116.16mm².

The Xiaomi Mi 12S Ultra is 13.1mm x 9.8mm, with a diagonal length of 15.9mm and an area of ​​128.38mm².

For comparison, the Evergreen IMX766, the official label is 1/1.56 inch (16.28mm), its imaging area is 8.16mm x 6.1mm, the diagonal length is actually 10.2mm, and the area is 50.1mm².

In this way, the imaging photosensitive area of ​​the Xiaomi Mi 12S Ultra camera is slightly better than that of the Sony RX100 series cameras, and it is better than the IMX766. The title of "the world's largest smartphone camera" is justified.

It's time to set a new standard

A one-inch sensor is not an inch. It was previously limited to a small circle like a camera. It originally had a certain threshold, which can also be classified as "image common sense".

However, with the development of smartphone images, the "common sense" of these small circles can easily lead to misunderstandings.

▲ True Lies

Until now, after watching Jerry's video, some people still think that the "one inch" of Xiaomi 12S Ultra is just a marketing word.

Likewise, as small devices such as drones and smartphones become more common, dpreview has once again launched an initiative to adopt a new dimensioning standard for sensor sizes.

In fact, as early as 2002, when CCDs began to replace camera tubes for imaging, dpreview clarified that the actual size of square sensors has little to do with traditional labeling.

Unlike the "clarification" 20 years ago, this time dpreview gives two options to reduce confusion and misleading.

▲ The real size picture of CMOS in the traditional one-inch size comes from: dpreview

Together with many imaging technology websites, publishers, and many YouTube channels, they write the "one-inch" sensor as Type 1, and the 1/1.56-inch of the IMX766 is Type 1/1.56.

The M43, APS-C, full-frame, etc. that already have fixed standards are still in use and will not change.

In fact, the labeling method of Type 1 has long appeared in Sony Semiconductor, and dpreview is also pushing the flow, promoting it, and calling on terminal manufacturers to also adopt it.

In addition, since Type 1 omits size information, dpreview is also launching readers to investigate whether to attach a specific size as a mark after Type 1.

And said that the real imaging area of ​​the sensor has a considerable impact on the image quality, and direct annotation can convey the most intuitive difference.

Such a clear and clear label completely gets rid of the legacy problems of image development and avoids the confusion of concepts.

The establishment of standards is not achieved overnight, but more like a process involving upstream sensor manufacturers, terminal manufacturers, product promotion methods, and consumer perceptions.

However, mature and reliable standards can indeed present real specification information, rather than covering up some information with "common sense".

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