Technical specification and knowledge expansion of mobile phone camera (taking Apple mobile phone as an example)

To learn photography, you also need to know the relevant technical parameters and principle concepts of the camera. Let's take iPhone6 as an example to explain the meaning of its camera parameters and help you understand some basic concepts and principles of photography.

Pixel and resolution are two basic terms and concepts that must be understood when learning digital images.

Pixels are elements of a picture. Pixel is the combination of letters and elements of a picture, which is the basic unit used to calculate digital images and the basic unit of resolution.

Image resolution determines how much information is displayed, measured by pixels in each direction, such as horizontal and vertical pixels, width and height pixels, etc.

Resolution can be classified in two directions: display resolution and image resolution.

Display resolution, that is, screen resolution, refers to the number of pixels that the display can display and measures the accuracy of screen images. Image resolution is an image composed of how many pixels, that is, the number of pixels contained in the image, which measures the accuracy of imaging and the image itself.

In general, dpi (dots per inch), line perimeter and pixels per inch can be used as units to describe resolution. At this point, the width and height of the screen can be known by conversion.

For example, the parameter "1334 x 750 pixel resolution, 326 ppi" of the display screen of iphone6 indicates that the display screen of iphone6 is 1334 pixels long, 750 pixels wide and 326 pixels per inch, so the screen of iphone6 is about 4.09 inches long (1334/326) and about 750/wide.

The main camera on Apple's mobile phone is the iSight camera. As for why it is called iSight camera, it may be the name given to its camera by Apple, or it may be designed by the iSight technology adopted by the camera. I don't know.

Take a photo with iphone6 and see the details of the photo. It can be seen that the image resolution of the photo is 3268 x 2448, and the calculation result is almost 8 million.

Accordingly, the resolution of photos taken by iphone6 camera in square mode is 2448 x 2448.

By pixel, the camera refers to the largest pixel of the camera. The maximum pixel of the iPhone6 camera is 8 million, and the pixel of the photo taken will only be smaller than this value, not larger than this finger.

As we know, the imaging mechanism of camera is pinhole imaging principle. When light and images are transmitted from the lens and projected on the surface of the photosensitive element, the photosensitive element will generate current, and the sensed content will be converted into digital data for storage.

The photosensitive material of the camera changes under the influence of light, so that the image is stored as a photo. The element that controls the incoming light is called the shutter, and the attribute mark that measures the sensitivity of the photosensitive element to light is called the sensitivity. The corresponding camera has two parameters: shutter speed and ISO sensitivity.

The size of a single pixel refers to the size of the photosensitive element of a single pixel. The larger the size of a single pixel, the larger the area of a single photosensitive unit, the stronger its signal-to-noise ratio and photosensitive ability, the better the imaging quality and the clearer the collected image.

The large size of a single pixel means an increase in exposure, and most directly, the low light environment will be much better.

The size of a single pixel is 1.5 micron, which means that the size of a single photosensitive unit is 1.5 micron.

Focusing, also known as focusing and aiming at light, refers to the process of changing the distance and the position of the distance through the camera focusing device to make the image of the object clear.

Digital cameras usually have auto focus, manual focus and multi-focus.

Auto-focusing is a way for the camera to drive the electric focusing device to focus according to the reflected light received by the sensor photosensitive element when shooting by using the principle of object light reflection.

There are two modes of autofocus: active autofocus and passive autofocus.

Active autofocus requires the camera to have a light emitting system, and the camera calculates the focusing distance according to the light emitted by itself after being reflected by the object, so as to drive the electric focusing device to focus.

Passive autofocus realizes autofocus by judging the actual imaging of the lens, without the need for a camera with a light emission system.

Generally speaking, SLR cameras have two autofocus modes at the same time, which automatically switch and complement each other.

Focus Pixels is phase detection, full name of phase detection autofocus, English is phase detection autofocus, and Apple calls it Focus Pixels.

Phase detection autofocus is a focus detection autofocus mode, which belongs to passive autofocus.

Corresponding to the focus detection autofocus mode, there is ranging autofocus; Corresponding to phase detection is contrast detection.

The camera focusing of Apple's mobile phone is automatic, because the focusing process takes a certain amount of time, so you need to wait for the focusing time before taking pictures to take clear photos.

Aperture is a device used to control the amount of light entering the photosensitive surface of the fuselage through the lens. The size of the aperture is expressed by F value, which plays a certain role in determining the amount of light entering the lens.

The f value is inversely proportional to the aperture size, and the larger the f value, the smaller the aperture; The smaller the f value, the larger the aperture.

It is also known from the formula that the aperture of a long focal length lens is larger than that of a short focal length lens to achieve the same aperture f value.

"? /2.2 aperture "means that the maximum aperture is 2.2.

Under the same conditions, the larger the aperture value, the better the camera quality.

Optical anti-shake relies on the camera's built-in precision gyroscope and a set of movable lenses to calculate and correct the instability caused by light deviation caused by hand shake, avoid blurring and ensure stable shooting effect.

Optical anti-shake is realized through the lens; The correct name of image anti-shake is CCD shift anti-shake, which realizes anti-shake effect through slight movement of photosensitive element.

After all, the optical image anti-shake function is an advanced anti-shake function. IPhone6 doesn't attack this function, but iPhone 6 Plus provides this function, which proves that the big body can also get a stable shooting effect.

IPhone6 also provides anti-shake function, and its parameter table has automatic image anti-shake function.

Flash is mainly used to fill the light, increase camera exposure, make up for the lack of light, improve the brightness of the picture, or remove stray light, so that the color of the photo can be restored more realistically.

The flash used by iPhone is called "True Tone" by Apple. Its dual True Tone LED fill light can not only provide more light, but also adjust the flash intensity and color temperature according to the color of the environment to provide more accurate light color.

Five-mirror lens is a lens composed of five pieces of glass.

Filters are used to achieve various special effects of images.

In the process of photography, infrared filters can be used to separate the infrared effect in the mixed light environment of visible light and infrared light. Its function is to filter and cut off visible light while allowing infrared light to pass through, which is called infrared shooting.

There is a lot of infrared and visible light in sunlight. Visible light will interfere with infrared shooting and make the picture overexposed. Adding infrared filter to filter visible light can get pure infrared effect.

When shooting in the dark environment of visible light, such as at night, infrared and visible light are very weak, so infrared rays are often strengthened when shooting.

Therefore, the function of the infrared filter of the camera is to separate the infrared effect in the mixed light environment of visible light and infrared light, so as to keep the visible light effect or infrared effect and make the photos taken pure.

The effect of separating visible light from infrared light is often achieved through a filter and a shielding mirror, so understanding is enough.

In the traditional camera photosensitive element, the photosensitive diode is located behind the circuit transistor, and the amount of light entering will be affected by occlusion. The so-called back-illuminated photosensitive element is to turn the original direction and let the light enter the photosensitive diode first, thus increasing the exposure and significantly improving the shooting effect under low light conditions.

That is, the lens is made of sapphire glass, which has the characteristics of wear resistance and correspondingly reduces the optical performance.

Anti-shake function is to prevent instability caused by light deviation caused by hand shaking, avoid blurring and ensure stable shooting effect.

HDR, the abbreviation of High-Dynamic Range, namely high dynamic range, also known as high dynamic lighting rendering, is a post-processing technology. For HDR LDR (low dynamic range) images with different exposure times, the final HDR image can be synthesized with the best detail LDR image corresponding to each exposure time, which can better reflect the visual effect in the real environment.

Dynamic range refers to the relative ratio between the highest value and the lowest value of electrical signals, which is reflected in the details that can be displayed in high light areas and dark areas. The larger the dynamic range, the richer the levels. To get HDR image effect, it is not enough to take only one photo. It is necessary to take a series of different photos of exposure value and synthesize a high dynamic range photo through software.

Automatic HDR photo means that the camera will automatically take multiple photos, and synthesize an HDR photo according to the multiple photos taken and save it as a shot photo.

When the iPhone6 camera shoots with HDR, the word "HDR" will appear on the yellow background at the bottom of the frame and above the white photo button. At this time, at least two photos will be taken, one is a natural photo and the other is an HDR photo. When viewing HDR photos, the word "HDR" will appear in the upper left corner.

Face recognition function applies face recognition technology to the camera to make it have the function of face recognition. When shooting a view, it can automatically identify whether there is a face in the current view. If a face is detected, it will automatically focus on the person's face to avoid out-of-focus and blurred photos.

The exposure control is automatic exposure. In this exposure mode, the camera will automatically control the shooting exposure. The sensor on the camera can automatically set the aperture value and shutter speed according to the intensity of reflected light from the scene, and the user does not need to do anything.

The maximum pixel of the camera is 8 million, so if you want to take a photo that exceeds the maximum pixel of the camera, you must take it in panoramic mode. Panoramic mode shooting is achieved by moving the lens horizontally and evenly.

The panoramic mode resolution of iPhone6 is up to 43 million pixels. We know that the lens height of iPhone6 is 3264 pixels, so the maximum photo length in panoramic mode is (43000000/3246 =) 13247 pixels.

Panoramic shooting instructions: Open the camera application of iPhone and swipe left in shooting mode to select Panoramic mode. After entering the panoramic mode, the picture-in-picture will appear on the screen, and we will be prompted to keep moving the iPhone while shooting. When shooting, we should pay attention to the operation skill of "keeping the arrow on the center line" to ensure the smooth connection of the panorama. After shooting, we can click the "Stop" button at the bottom to stop shooting. PS: Panoramic photos don't have to be 4300 pixels.

That is, it supports the continuous shooting function.

Instructions for use: The continuous shooting function of iPhone can be realized by holding down the white camera button. Quickly click the white photo button to take a single photo, and press and hold the white photo button to take continuous photos.

Continuous shooting snapshot is very useful in shooting moving pictures, and you can choose ideal action photos from multiple photos.

When viewing continuous shooting Snapshot in Photos, a picture will be displayed with the words "continuous shooting Snapshot (XX photos)" on it, indicating that it is similar to a photo folder, and the words "Select ..." below it. Click "Select" to view the photos of continuous shooting one by one.

Note: Apple's continuous shooting snapshot only takes one photo, and one photo is transmitted when transmitting, not all photos of continuous shooting. Therefore, before using it, it is best to delete and select the photos of continuous shooting.

Light focusing refers to half-pressing the shutter to complete focusing without shooting. When iPhone takes photos, tap the viewfinder, which can be used for metering and focusing. When autofocus is not ideal, tap focusing can be used to achieve better metering and focusing effects.

Instructions for use: The shutter of the camera has a motion stroke from pressing to triggering shooting. Most autofocus cameras will focus first when the shutter is pressed, usually accompanied by a focus completion prompt or instruction. After focusing, press the shutter again to finish shooting. Therefore, in order to get a good shooting effect, we must first focus on the camera. If you press the shutter too fast, the focusing process will not be completed well, and the photos taken will be very poor.

When taking photos with a mobile phone camera, you can get better photometric focus and ensure the shooting effect.

The function of photo geotagging is to attach GPS information to photos, so as to show the geographical location of the photos taken.

Use of geographical marking function of iPhone photos: Open the location service of iPhone, find the camera and photos that need to be located in the following program, and check the use period in the location information that allows access, so that you can add geographical location information to photos when taking photos, and display photos according to the shooting area when viewing photos.

Geographical location information can also help to recall the scenes taken by photos and help to organize photos according to location.

Timing mode supports setting countdown shooting mode.

The use of iPhone6 camera timing mode: iPhone6 camera supports 3 seconds and 10 seconds countdown shooting. Turn on the camera, click the third clock icon above the viewfinder, and select the timing mode, which is off by default.

Timing mode is still very useful when taking selfies.