Photography starts with mobile phones (05) The key factors that affect mobile phone photography.

Photography starts with mobile phones-content

1. Mobile phone is the best entry tool for photography.

2. The difference between mobile phone and SLR camera photography

3. What is a good photo?

4. Talking about the art of photography

5. Key factors affecting mobile phone photo taking

6. Basic theory of exposure

7. Understand photographic composition

8. Master the composition of portrait photography

9. Composition of actual combat scenes

A mobile phone photo is mainly generated by hardware (camera component) and software (algorithm) on the mobile phone. In order to understand the factors that affect mobile phone photography, we must understand the principle and context of mobile phone photography.

Among the components of mobile phone camera, lens, DSP (Digital Signal Processing Chip *) and sensor are the most important three parts.

Lens is the second factor that affects image quality after CMOS chip. Its structure is a lens structure, consisting of several lenses, which can be generally divided into plastic lens (P) or glass lens (G). Of course, the so-called plastic lens is not pure plastic, but resin lens. Of course, its optical indexes such as transmittance and sensitivity are not comparable to those of coated lenses.

The more lenses, the higher the cost and the better the relative imaging effect. And glass lenses are more expensive than resin. Therefore, a good quality camera should use multi-layer glass lenses.

The aperture number f is the key optical index of the lens. It represents the amount of light entering. The lower the f value, the wider the use range of the lens. For example, Huawei P20 Pro rear Leica three shots: 40 million pixels (wide angle, f/ 1.8 aperture)+20 million pixels (ultra wide angle, f/ 1.6 aperture)+8 million pixels (telephoto, f/2.4 aperture).

The larger the aperture, the more light reaches the sensor through the lens, and the brighter the image, otherwise the darker the image. Therefore, the imaging advantage of large aperture is more obvious in night shooting or dark light environment.

Aperture not only controls luminous flux, but also controls depth of field. In our daily life, we often see photos with strong blurred background, which not only highlights the shooting focus, but also has a very beautiful artistic sense, which is called depth of field. The larger the aperture, the smaller the depth of field, and the more obvious the background blur effect.

The function of DSP is to optimize the digital image signal through a series of complex mathematical algorithm operations, and finally transmit the processed signal to the display.

The sensor converts the light from the lens into an electrical signal, and then converts it into a digital signal through internal analog-to-digital conversion. The light reflected by the photographed object enters the system, passes through the lens, reaches the image sensor and is converted into a digital signal. Digital signal is stored by DSP digital signal processing chip and transmitted to the screen, forming the same image as the photographed object.

The so-called "XXX megapixels" actually refers to the resolution of the camera, and its value is mainly determined by the number of pixels in the camera sensor (that is, the minimum photosensitive unit). For example, 5 million pixels means that the sensor has 5 million pixels, which is the same reason that the pixel number of the mobile phone screen determines whether the screen resolution is 720p or1080 p.

The higher the camera pixel, the larger the picture size. If the current mainstream mobile phone screen is1080p (1920×1080 pixels), then the 4208×3 120 pixel photos obtained by13 million pixel camera are still 8 million pixels. All of them are beyond the interpretation range of 1080p screen, and will eventually be displayed as 1920× 1080 pixels, so there is no difference in the clarity seen by naked eyes. Of course, if you watch it on a screen with 2K and 4K resolution, you can still see the difference.

One advantage of high pixels is that it is convenient to cut photos later. If the pixel is high, there is more room for cropping. The other is that when printing photos, you can output a larger size. According to the conventional printing standard of 300 pixels/inch, a 4,208× 3120 pixel sample taken by a camera with a pixel of130,000 can print a photo of 17 inch.

According to the scoring ranking published by camera testing agency DxOMark, Samsung's total score of S 10+ is 109, and its selfie score is 96, ranking first in DxOMark's selfie list. S 10+ tied for the first place with Huawei Mate20 Pro and P20 Pro, with both scores of 109. (In the case of the same score, DxO adopts alphabetical sorting system).

Samsung S 10+ is equipped with a 6.4-inch AMOLED screen, and the rear is upgraded to three shots, namely:12 million pixel main shot, pixel size 1.4μm, aperture f/1.5-2.4; 16 megapixel super wide-angle sub-photo; 12 megapixel telephoto lens, supporting 2 160P/60fps video shooting. The main camera still uses the same 1/2.55 inches and 12MP hardware as S7 edge in 20 16.

The color lenses on Huawei P20 Pro and Mate 20 Pro adopt IMX 600 CMOS, the size is11.73 inches, and 40 million pixels are arranged as Quad Bayer. IMX600 was jointly developed by Sony, Huawei Finland Research Institute and Huawei Japan Imaging Research Institute, which took more than two years.

With the release of Sony IMX586, this is a non-customized version of the sensor, which can be purchased by all mobile phone manufacturers, with a total pixel of 48 million. The size of the sensor is 1/2 inches, and it uses the same "quad Bayer" 4-pixel homochromatic filter as IMX600. CMOS area and single-pixel illumination ability are close to IMX600. The main cameras of Xiaomi 9 and Glory V20 all adopt the mainstream Sony IMX586. Xiaomi 9 ranked fourth in DxOMark, only 2 points away from the first place.

Before the official launch of IMX586, the flagship CMOS commonly used in Android flagship models were IMX380 and IMX363. The former is used for Huawei P20 and Meizu 15, while the latter is used for vivo NEX, nut R 1 and millet MIX2S. In addition, Sony also introduced IMX400 supporting 960FPS slow-motion video for Sony Xperia XZ2 and other models. Let's take a look at the specific parameter comparison of these CMOS models:

The number of lenses is not the key to determine the image quality. Previously, Google Pixel 2 used a single camera and has been performing well. It once dominated the DXO leaderboard for a long time with 98 points. Now the new Pixel 3 is still only equipped with a12.2 megapixel main camera, which supports dual-pixel dual-core focusing and F 1.8 aperture. IPhone XR is also a single camera, and its score on the DXO leaderboard is 10 1.

There are several reasons why the mobile phone rear camera integrates the second and third cameras. One is the "wide angle+telephoto" led by iPhone. By switching cameras, the shooting function of 2 times lossless zoom can be realized, which can increase the depth of field for portrait photos and improve the imaging quality when users zoom in on the subject.

The second is the "color+black and white" of Huawei mobile phone, which brings more light with black and white camera, and the "main camera+auxiliary depth of field" of vivo mobile phone. Monochrome cameras enable users to take black-and-white photos without using any filters, or add more details to color photos, which is reflected in the blurred background.

The third scheme is that Huawei P20 Pro combines the first two schemes and uses three cameras of "color wide angle+black and white wide angle+telephoto" to achieve high-quality performance at the professional camera level.

Huawei P20 Pro rear camera includes all three cameras.

Three cameras is a scheme to catch up with cameras at present, and there may be a better scheme to replace this design in the future. When it comes to the internal algorithm and data processing ability of the camera, it is easier for the mobile phone to achieve complex algorithm image synthesis than the camera, which also makes it possible for the mobile phone to barely reach the shooting level of the camera when the sensor size is not as good as the camera.

Although the screen color of mobile phone can't participate in the shooting of photos, it is the most important display platform for photos. The display effect will directly affect our judgment of a photo.

When mobile phones with different prices display the same picture, the color performance of high-priced products is often more realistic and gorgeous. The reason behind this is that the color gamut parameters of different screens are different. The maximum color range in the figure below is the color that can be distinguished by human eyes, and the triangle range is the color range included in the sRGB standard.

The color gamut standard used in mobile phone screens is often based on sRGB. The higher the percentage, the better the screen quality. The iPhone series insists on using a screen close to the full sRGB color gamut, and does not exceed the sRGB color gamut of 100%. Samsung series mobile phones, using AMOLED screen, provide 100% DCI-P3 color gamut, which has exceeded the sRGB range.

From the point of view of "real comfort", in fact, the closer to the color gamut of 100% sRGB, the better. Too high will appear rich (supersaturated), too low will lead to inaccurate color reproduction.

Contrast reflects the brightness when the screen displays colors. The higher the contrast, the brighter the color display. Generally speaking, the screen contrast of a good LCD mobile phone is about 1500: 1, while organic spontaneous light screens such as AMOLED and organic light-emitting diodes will be higher in color gamut and contrast than LCD screens due to their inherent advantages.

General 1080P resolution LCD screen will be better than ordinary OLED screen. The OLED screen with the resolution of 1080P is only Samsung's super AMOLED, and the AMOLED screen with the resolution of QHD2K (* * * x1440) should have the best display effect.

Compared with traditional SLR cameras, mobile phone camera software can provide more advanced image processing technology, and can be continuously upgraded and improved by using artificial intelligence technology.

Google's Pixel 3 is only equipped with a12.2 megapixel camera. From the parameter point of view, there is nothing special. The reason why Google continues to use a single camera should be that it is very confident in its own algorithm. When taking pictures, the camera will take many photos of different colors and finally synthesize the best. At the same time, the mobile phone will start a function similar to video recording. Before the user presses the shutter, the phone will take a picture. In this way, if the user is not satisfied with the photos he has taken, such as closing his eyes and foreign objects entering the lens, he can choose the photos taken some time ago.

Pixel3 mobile phone uses AI technology to separate the background from the characters, which realizes the functions of separate color matching and adjusting the intensity of background blur, and also provides autofocus tracking function. Even if the focused object moves, the camera can lock the focus on it. It also brings better low-light shooting effect, which is also achieved through multi-Zhang Hecheng, and Google also uses machine learning to enhance the color of photos.

Huawei's new AI algorithm fuses the data of three cameras, plus Leica's zoom system and advanced anti-shake performance, Huawei P20 series can rank first in DXO mobile phone rankings.

Samsung S 10+ uses the same camera as S9 a few years ago, while Huawei P20 Pro uses the most advanced IMX600, which shows the importance of image software processing technology.

It is hard to say what level mobile phone shooting will develop in the future, but it is foreseeable that the shooting function of mobile phones will be more popular and smarter than cameras.

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