#Ultra-Widecamera

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Pixel and matrix size, its resolution and aperture in the smartphone camera

The popularity of smartphones has been growing rapidly for over 10 years. Of course, companies adequately respond to huge demand, constantly improving their models. Traditionally, the competitiveness of any device depends on its price, functionality and specs. The price and functionality are not covered in this article. But in general, competition forces companies to expand intensively functionality and pursue flexible pricing policies. As a result, a modern budget smartphone worth several hundred dollars already provides opportunities that seem unlimited compared to models 5 years ago. Blackview MAX 1 Projector Mobile Phone with a projector function, Desktop Mode in Android Q 10 and foldable smartphones perfectly illustrate this trend. In fact, the modern smartphone has become a universal pocket PC with fairly high-quality media functions, including a camera, projector, etc. Of course, competitiveness requires continuous improvement of all components, including smartphone performance, camera, Smartphone Storage, OS, screen etc. In particular, the improvement of cameras is developing in two directions. First, companies increase the number of different cameras, expanding shooting opportunities. As a result, modern multi-camera smartphones provide high image quality when shooting in almost any conditions. A list of the most popular add-on modules includes Ultra-Wide, Telefoto, Depth and ToF cameras. Today even budget models often use two cameras. Modern flagships usually have three or more modules. Moreover, Sony announced a smartphone with an unprecedented 8 cameras.

Secondly, companies continue to traditionally improve the main specs of matrices and lenses. This article offers a more detailed analysis of this aspect.

Resolution, Pixel size and aperture

As known, the matrix forms an image using photosensitive cells (photosensors). 1 MP corresponds to a million photosensors on the matrix. They determines the resolution of the matrix and directly affects the image quality. A few years ago, smartphones have mainly used a 0.5-megapixel, 1.3-megapixel or 2-megapixel matrix. Only some flagships had 5-MP cameras. The rapid development of the production technology of photosensors has radically changed the situation. Modern models already use matrices with a resolution of 8 MP to 40 MP and even more.

The pixel size directly affects the number of absorbed photons during exposure. Accordingly, the photon flux capture efficiency is different for matrices with different pixel sizes. This factor directly affects image quality. Its gradations are: - 1.55 μm-1.40 μm - high quality even in low light; - 1.40 μm-1.22 μm - high quality in normal lighting, image noise in low light; - 1.12 μm or less - high quality only in bright conditions. But increasing the pixel size with the same resolution requires an increase in the matrix size and optics, which increases the thickness and width of the smartphone. Therefore, companies are forced to constantly seek compromise solutions. Bright detailed images require a powerful light output, which depends on the aperture (degree of lens openness).

Accordingly, a wide aperture absorbs more light flux. Its size is denoted by "f". Wide aperture provides macro photography, bokeh effect, etc. The effect of aperture on quality: - f / 2.6, f / 2.4 - low quality; - f / 2.2, f / 2.0 - usually used in budget models; - f / 1.8, f / 1.7, f / 1.6 - the optimal aperture.

Image sensor size

The matrix is a chip with photosensitive photodiodes. As known, a photodiode under the influence of light forms an electrical signal, which is subsequently converted into a digital signal. In fact, the matrix performs the function of a film in traditional cameras. In the future, information about the image goes to the processor, which converts it and sends it to the smartphone’s storage. On average, this process lasts 0.2-0.3 seconds. At the same time, the picture quality directly depends on the matrix size. Modern models use matrices with the following diagonal: - 1/3"- budget smartphones; - 1/2.9", 1/2.8" - mid-level models; - 1/2.6", 1/2.3" - flagship smartphones.

For example, the diagonal of a 12-megapixel Sony IMX386 matrix in Xiaomi Mi Mix 2 is 1 / 2.9" (6.2 mm) and the pixel size is 1.25 microns.

The ratio between the size of the matrix and pixel

Of course, a large number of pixels (resolution) requires an increase in their density.

But for a constant matrix size, this requires a reduction in pixels size with a decrease in absorption of light by each of them. Thus, only the choice of the optimal ratio can ensure maximum image quality. For marketing reasons, most companies often do not specify pixels size, indicating only the matrix resolution. But the resolution does not characterize the efficiency of light absorption, and, as a result, the real quality of the images. Today, companies are experimenting with this ratio. Samsung Galaxy S6 perfectly demonstrated very successful combination.

With the same specs, it clearly wins compared to the iPhone 6.

In addition, Samsung Galaxy S7, S8, S9 with a 12-megapixel matrix also demonstrate excellent quality due to the large pixel size.

Super Pixel (Quad Pixel, Quad Bayer, TetraCell) technology

Having reached a huge resolution (48 megapixels, 64 megapixels and more), companies began to look for other ways to further improve the camera. As a result, Super Pixel technology using Pixel Binning was developed. In fact, this algorithm combines four small pixels into one large pixel using filters.

Almost all leaders use this technology. Sony calls it Quad Bayer, Samsung uses the TetraCell term. Mixing pixels eliminates the problem of low light. The algorithm combines RAW data from four pixels into one effective super-pixel, providing the maximum amount of captured light while reducing image noise. Of course, it reduces the actual image resolution. For example, a 24-megapixel camera with Super Pixel technology can provide a real resolution of only 6 megapixels. Therefore, cameras with low resolution rarely use this option. Its effectiveness is manifested in 40-megapixel matrices and higher. In this case, the algorithm improves quality in low light conditions by reducing over-resolution. In addition to reducing resolution, this technology also eliminates the output of the RAW (DNG) format due to data loss during the Pixel Binning.

OIS and autofocus

Many modern cameras use OIS (Optical Image Stabilization) to increase clarity and improve focus when shooting in motion or in low light.

In fact, OIS provides amortization to compensate for camera movements during movement. The optical stabilization mechanism smoothes shaking hands or movement while walking. Functionally, OIS replaces the traditional tripod. Budget models often use digital stabilization instead of the more efficient and expensive optical stabilization. In this case, the algorithm smoothes gradations of blurry frames. In addition, almost all modern cameras have autofocus on one or more objects. Today, companies use contrast, phase and laser autofocus. But laser autofocus provides maximum efficiency.

Conclusion

1. The resolution of the image sensors in the cameras of smartphones has almost reached its maximum. Its further increase is already limited by a decrease in captured light due to a decrease in pixel size. Apparently, further improvement of the cameras will be based on increasing the matrice size and improving the signal processing algorithms. 2. On the other hand, even medium-budget models provide high enough quality for amateur photography. Many expensive smartphones are already successfully competing with traditional cameras for picture quality. This video demonstrates latest innovative Sony IMX686 image sensor for smartphones. Read the full article

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Overview of cameras in the multi-camera smartphones

For several years, smartphones have been steadily leading in popularity in the consumer electronics segment. Enormous competition encourages companies to constantly expand the functionality of their models. For example, companies already offer Projector Mobile Phones with a projector function, including Blackview MAX 1 Projector Mobile Phone.

But as before, the choice of optimal smartphone depends on its price, brand and specs, including OS, smartphone performance, Smartphone Storage, screen, etc.

Smartphone cameras

Of course, the camera also belongs to the most important specs of a modern smartphone. In recent years, almost all leading companies have been actively improving the cameras of their models, including by increasing the number of modules. As a result, today the market offers smartphones with different numbers of lenses in different combinations. Many modern phones, including budget models, already use two modules, but many flagships have 3 or even 4 cameras. For example, in 2018 Samsung introduced the Galaxy A9 (2018) with Main Camera and three additional, including Ultra-Wide, Telefoto (optical zoom), and Depth cameras.

But at the end of February at the MWC-2019 in Barcelona, HMD Global already introduced the Nokia 9 PureView with five cameras.

Nokia 9 uses Zeiss optics, provides a 12-MP picture, saves the image in RAW format, providing its editing on a smartphone. It has two color 12-MP, f / 1.82 cameras and three black and white with similar parameters. In addition, the smartphone uses a 20-MP front camera. Finally, Sony announced a model with 8 cameras, including 20-MP f/2.4, 48-MP f/1.2 and f/2, 16-MP f/2.4, 8-MP f/2.4, 12-MP f/1.2 and f/2.4, and 0.5-MP ToF lenses on the rear panel.

In addition, it has front 10-MP and 0.3-MP ToF cameras providing Portrait Mode.

Basic cameras

Functionally, smartphones with dual cameras can be divided into several types. The second camera can be used as a Depth or Ultra-Wide, for zooming or night shooting (monochrome camera). Additionally, such models can collect data for portraiture or other effects, eliminating the need for a dedicated sensor. Thus, dual cameras provide greater flexibility, providing improved quality for different shooting conditions. For example, Telephoto lens provides background blur and optical zoom without loss of quality. In 2016, Apple first used it in the iPhone 7 Plus. The experiment was successful and today many companies use it. Until 2019, their optical magnification did not exceed 2x or 3x. But today the Huawei P30 Pro, Oppo Reno and Xiaomi Mi Mix 4 already support 5x.

A wide-angle camera provides 120 degrees, capturing more objects in the frame. In 2016, LG first introduced the flagship with such a lens. At the end of 2018, Samsung and Huawei began to install a similar module in some expensive models. Today, the Galaxy S10 uses an ultra-wide 123 degree lens.

The black and white camera works in tandem with the main module and provides improved light capture in low light conditions. In 2018, Sony installed such a camera in the Xperia XZ2 Premium. In the 2018 Oppo RX17 Pro and Honor View 20 was first used the 3D ToF (Time of Flight) stereo camera. The 3D sensor provides scanning of objects to form a 3D image.

The number of cameras in the modern smartphone

Of course, adding a third camera further expanded the functionality. As known, Huawei P20 Pro was the first such model. It has a 40-megapixel main module, a 8-MP telephoto camera with 3x zoom, and a 20-megapixel monochromatic camera. The combination of such optics and effective software provided excellent zoom and high quality even in low light conditions.

Нuawei has previously already used hybrid technology with a monochrome camera to improve images in low light and to increase digital zoom. But the combination of a 3x telephoto lens and a 40-megapixel high-resolution matrix in the P20 Pro ensured high quality even for 5x zoom. The LG V40 also uses three cameras, including a 12-MP main camera, a 12-MP lens with 2x zoom, and a 16-MP wide-angle camera. This combination provides excellent quality for almost any shooting condition.

However, Samsung took the next step by adding a fourth module. Its Galaxy A9 (2018) uses main, telephoto, wide-angle and 5-megapixel Depth modules. Of course, such a decision may seem controversial because the wide-angle and zoom cameras provide information about the frame depth. For example, the Live Focus feature in Galaxy Note 8, 9, and S9 Plus uses telephoto camera data. But the addition of a special sensor exclusively for frame depth increases the detail, improving the image quality in portrait mode and creating a bokeh effect.

For this purpose, other companies often use a monochrome camera instead of the Depth module.

Dimensions

Unlike the large cases of traditional digital SLR cameras, smartphones have a very limited internal volume. Its slim body should include a screen, chipset, battery and other components. Therefore, companies use very compact matrices for smartphone cameras. As a result, they capture significantly less luminous flux compared to the much larger matrices of full-size cameras. Today, developers use sophisticated image creation algorithms, including Image Averaging, etc. In general, adding new modules requires reducing the sensor size of each camera, reducing the size of other components, or changing the phone design. But the first method radically reduces the image quality, and the second method degrades other specs of the device. Thus, a design change remains the only acceptable way. Perhaps new models with a large number of cameras will be thicker or will have a protrusion near the lenses. In addition, this trend has another aspect. A similar situation was already in the photo industry segment. A few years ago, Light introduced a 52-megapixel Light L16 with 16 cameras.

The focal length of their lenses varies from 28 to 150 mm. Theoretically, it should provide high-quality zoom with a resolution of up to 52 MP. Unfortunately, the low speed of creating a picture, the need to use the Light Lumen app for most settings, and the huge variation in frame quality have radically limited its popularity. Therefore, adding cameras without high-performance software can create many additional problems.

Conclusion

Fierce competition encourages companies to actively expand the functionality of smartphones by increasing the number of cameras and improving their collaboration algorithms. Of course, this aspect affects the choice of the optimal model. Probably, at some stage, factors of price, device size and control complexity will limit this trend. But modern models already offer from two cameras in the mid-budget segment to an unprecedented 8 cameras in the new Sony smartphone. This video illustrates the effectiveness of dual camera operation in the Xperia XZ2 Premium. Read the full article