Don't be a cainiao! Don't confuse camera parameters

[Zhongguancun online Camera channel original] at present, the camera market, the cheapest 30 pieces, expensive hundreds of pieces, and some even to more than one thousand pieces, the gap is so big, why? Is the seller shouting price over the sky? Or is there a big gap in costs? Or for other reasons? When you purchase a camera, you must first check the camera configuration. Just like installing a computer on your own. However, many users are confused about the choice of camera parameters. Today, let's take a look at the camera packaging parameters, so that you can choose to know yourself and know yourself.

 

 

 

 

Camera Overview

Cameras (CAMERA), also known as computer cameras and computer eyes, are widely used in video conferencing, telemedicine, and real-time monitoring as a video input device. In recent years, with the development of Internet technology and the continuous improvement of network speed, coupled with the maturity of photosensitive imaging device technology, it has been widely used in the manufacture of cameras, this reduces the price to a level that ordinary people can afford. Ordinary people can communicate with each other through cameras with images and sounds on the Internet.

Camera category

Cameras are classified into two categories: digital cameras and analog cameras. A simulated camera can convert analog video signals generated by video capture devices into digital signals and store them in a computer. The video signal captured by a simulated camera must be converted to a digital mode through a specific video capture card, and then compressed before being converted to a computer. The digital camera can directly capture images and transmit them to the computer through strings, parallel ports, or USB interfaces. Currently, cameras in the computer market are dominated by digital cameras, while digital cameras are dominated by USB Digital cameras using new data transmission interfaces. Most of the products currently on the market are such products. There is also a product that works with video capture cards, but it is not currently mainstream. Due to the rapid popularization of computers and the high overall cost of analog cameras, the transmission speed of USB interfaces is much higher than that of serial ports and parallel ports, therefore, the current market hotspot is the USB interface digital camera. The following mainly refers to the digital camera with USB interface.

How cameras work

The working principle of the camera is roughly as follows: the scene is projected to the image sensor surface through an optical image generated by the lens (lens), and then converted to an electrical signal, after A/D (modulus conversion) after conversion, it becomes a digital image signal, which is then sent to the digital signal processing chip (DSP) for processing, then transmitted to the computer through the USB interface for processing, and the image can be seen through the display.

The working principle of a camera determines the image quality of a camera. In terms of hardware, the first is the camera. Next, let's take a look at the camera lens.

　　Page 2nd: Camera Lens details

Lenses are an essential part of all imaging devices. Most consumers will also know that they are the first key to camera imaging, but do not know how to focus on the quality of lenses. Generally, there are three types of cameras based on materials. The camera lenses are divided into plastic, glass-plastic, and glass-glass, the best thing here is glass, because it has a large passthrough coefficient. Generally, a good lens also has a large passthrough diameter, when the light is not good, you can also get a good result, but the price is high (a penny of money ). Shujiao is almost accessible, but the price is low, which is also recognized by some low-end users. There are not many compounds on the market, so I will not detail them here.

 

 

 

 

Generally, cameras use lenses such as 1 P, 2 p, 1g1p, 1g2p, 2g2p, and 4G. The more lenses, the higher the cost. Generally, good cameras on the market use four glass-structured lenses, which are commonly known as 4G lenses. Some, coupled with a layer of Iris enhancement, are called 5g lenses.

 

The quality, price, and imaging effect of different lenses are also very large. How should we identify them? To put it simply, the amount of light passing through the glass lens can be used for identification. The F value is used to express the lens light usage. The smaller the F value, the more light the lens passes through at the same time. The more saturated the imaging color, the better the lens. Therefore, when selecting a lens, the F value must be smaller. Currently, the fvalue of the camera lens on the market is generally about 2.0, and the fvalue of the best camera lens is 1.8. This type of camera imaging is clear and smooth, but the price is relatively high.

The lens usually has two important parameters. One is the aperture, which is a device installed on the lens to control the amount of light that reaches the sensor through the lens. In addition to controlling the amount of light, the aperture also has the function of controlling the depth of field, that is, the larger the aperture, the smaller the depth of field. The other is the focal length, which is basically the distance from the center of the lens to the clear image formed on the sensor plane. The focal length of the lens determines the size of the image formed by the object taken by the camera on the sensor. Assuming that the same object is taken at the same distance, the longer the focal length of the lens, the larger the image formed by the object.

Through the above introduction, we are looking at some product parameter introductions, such as the lens: 5-glass lens. It should be easy to understand now. Because the camera is used for online chat, the imaging speed is also very important, and the imaging speed depends on the overall configuration of the camera. Therefore, not only the camera, but also the configurations of other camera components determine the quality of the camera, next, let's take a look at the second important part-the sensor, also known as a photosensitive chip.

　　Page 1: details about the sensor used by the camera, also known as the photosensitive Chip

A sensor is also called a photosensitive chip. We often say that a digital camera's sensor is equivalent to a traditional camera's film. It is used to receive light from a lens, and a device that converts these optical signals into electrical signals. Currently, two core imaging components are available for digital cameras: CCD (electric lotus root) components and CMOS (Complementary Metal Oxide conductor) devices.

 

 

 

 

Camera sensor chip

CCD is expensive, but the imaging pixels are high, the resolution is high, and the color reduction coefficient is high. Due to the limitations of the current broadband, using CCD will cause the image to be too large to be transmitted between networks, therefore, cameras seldom use such photosensitive chips. Low CMOS price, low power consumption, and fast response. In products using cmos as photosensitive components, the automatic gain reinforcement technology of image light sources, automatic brightness and white balance control technology are adopted, advanced Image control technologies, such as color saturation, contrast, edge enhancement, and Gamma Correction, can achieve the same effect as CCD cameras and meet the needs of the current market environment, therefore, CMOS is widely used for cameras.

Many photosensitive sheets on the image sensor indicate that the sensor can sense more details of objects, making the image clearer. To improve the image definition, in addition to generating elements in image processing, they can convert light into a charge to form an electronic image corresponding to the scene. In a sensor, each sensor corresponds to a pixel. The more pixels there are, the more sensor pixels there are. Increasing the number of sensor sensors is also a major way to increase the number of sensor pixels.

　　Page 4th: Camera "heart"-Details

The main control chip (DSP) is used to compress, transfer, and restore images, that is, the smoothness of images. A good DSP can produce a very smooth picture and occupy a small amount of CPU resources. There are many DSP manufacturers and the most popular ones on the market are: Star micro

 

 

 

 

Therefore, for consumers, a camera DSP chip with the same core function as a computer CPU is the most critical factor affecting camera performance. Therefore, a camera has a good DSP "core ", its performance will certainly not be poor. How to identify a camera's master chip is also an important knowledge for purchasing cameras. Right-click "my computer"-"manage"-"Device Manager"-"image processing device" and double-click any camera device, in the "details" column, you can see the specific information, and then you can go to the Internet to find the response to the master chip information, always judge whether it is good or bad.

 

What is the master chip? A dsp chip, also known as a digital signal processor, is a microprocessor with a special structure. The DSP chip adopts a Harvard structure separated by program and data. It has a dedicated hardware multiplier and is widely used in pipeline operations to provide special DSP commands, it can be used to quickly implement various digital signal processing algorithms. However, compared with general-purpose microprocessor, other general functions of DSP chip are relatively weak. The DSP converts digital signals to video images on the camera and transmits data with the USB bus.

In addition, the DSP chip is also the main factor affecting the video capture speed of the camera. The 0.3 million-pixel product must reach a speed of 25-30fps (25-30 frames per second) at a resolution of 640*480, a dsp chip with powerful performance is essential; otherwise, it can only reach 15 FPS (15 frames per second. But sometimes this problem is a bit contradictory, as we all know that for video chats, even in a broadband environment, the specific speed is more affected by the network environment and network speed, due to the domestic network environment, it is difficult to get 25 frames per second at a resolution of 320*240 or even lower. It is also lucky to reach 15 frames per second (15 frames per second is basically smooth ). Of course, this is only for chatting. In general LAN Video applications and home imaging applications, a more powerful DSP chip is necessary, and the technology development trend is also true.

Let's talk about the camera's image resolution/resolution, that is, the number of pixels that we often call a camera.

　　Page 1: camera pixels

Pixels, whether a camera or a digital camera, are one of the main performance indicators. The so-called pixel refers to the number of photosensitive units on the camera's photosensitive elements. The more photosensitive units, the more image information the camera captures, and the higher the image resolution, the clearer the screen image. Using the pixel value, we can calculate the maximum image resolution. For example, if the maximum resolution of a camera is 640x480, then the pixel is 640x480 = 307200, that is, 0.3 million pixels.

 

 

 

 

In practical application, the higher the pixel of the camera, the better the quality of the captured image, but on the other hand, the higher the pixel, the better. For the same image, the higher the pixel, the higher the resolution image capability of the product, but the larger the data volume recorded by the product, the higher the requirements for storage devices, therefore, the current mainstream products are used in the selection of region.

 

Currently, most mainstream cameras on the market use 1.3 million pixels, which means there are about 1.3 million photosensitive units in the sensor. The corresponding imaging resolution is 1280x1024 (that is, 1310720 pixels ). The resolution of the camera is not exactly the same as that of the monitor. The camera resolution is the ability of the camera to parse images.

There is no absolute relationship between the pixel height of the camera and the image definition. Especially for cameras with hundreds or even tens of millions of pixels through software interpolation, the actual effect is likely to be similar to that of hundreds or even tens of millions of pixels.

Currently, common camera pixels include 0.1 million, 0.3 million, 0.5 million, or even 0.8 million and 1.3 million.

Camera technical indicators

Resolution ):

1600x1200, or 2 million pixels

Sxga (1280x1024) is also called 1.3 million pixels

XGA (1024x768) is also called 0.8 million pixels

Svga (800x600), also known as 0.5 million pixels

VGA (640x480), also known as 0.3 million pixels (0.35 million refers to 648x488)

After introducing the core hardware of the three cameras, we know that the camera's imaging quality is not only the lens, the camera's photosensitive chip, but also the main control chip determines the camera's quality. Next we will introduce the number of frames, which is another factor related to imaging speed.

　　Page 1: Number of frames on the camera

Simply put, the number of frames is the number of frames that transmit images in one second. It can also be understood that the graphic processor can refresh several times per second, which is usually expressed by FPS. We all know that if the video playback speed reaches 30 FPS (30 frames/second), in fact, each frame is a static image, and the rapid continuous display of frames forms the illusion of motion, the naked eye will not feel the pause of the screen, and a higher frame rate can produce smoother and more realistic animations. The more frames (FPS) each second, the smoother the displayed action.

 

 

 

 

However, the number of frames is also affected by other elements. For example, when the image resolution increases, the video speed decreases sharply due to network bandwidth limitations. Different images require different capture capabilities. The maximum resolution of captured images by mainstream digital cameras is 640 × 480. However, in this resolution, the screen may be broken, the capture effect cannot reach 30 FPS. When the resolution is 320 × 240, the combination of hardware and software may achieve the standard rate of capture.

 

Therefore, the complete video capture speed is only a theoretical indicator. For frame rate, you can find an object to shake up and down in front of the camera (the swinging speed should not be too fast) to see if the image delay is serious? If the image can be displayed in a coherent manner, it can basically reach 30 FPS.

　　Page 7: whether the camera has the focusing Function

Generally, a good quality camera lens must have a focus function. The focal lengths of many cheap cameras are fixed. That is to say, the camera can only take clear images at a fixed distance, no clear image can be obtained once it is too close or too far.

A high-quality camera lens can adjust the focal length manually, so that no matter where you place the camera, you can get a clear image after adjusting the focal length, generally, we can use a adjusting device that is able to adjust the outside of the lens.

Currently, some high-end camera products have the auto focus function. Important to make our video chat clearer and easier.

　　Page 8th: other camera tips

　　Data Transmission Interface

Since Windows 95 and its support for USB interfaces, USB has developed rapidly. At present, USB has become the standard interface for cameras. This connection method is easy to use and supports hot swapping. The devices use their own reserved interfaces separately, do not compete for PC resources with other devices. For the previous 0.3 million pixel-level cameras, the transmission rate of the USB interface can fully meet the needs. If you want to purchase a camera with a million pixel-level, you 'd better choose the USB interface. However, if you use these products on the Internet, if your network speed is not fast enough, the transmission rate still does not go up.

In addition, factors that users can consider when purchasing cameras include software, built-in microphones, angle adjustment, base fixation devices, static shooting, and so on, which can bring a lot of convenience to our use. Among them, the app that comes with the camera is an important part, and many manufacturers have provided images and electronics such