How does a digital camera work?

The working principle of a digital camera is as follows: firstly, the light is received through the lens, then the received light is converted into an electrical signal through a photographic element called CCD (sometimes using CMOS sensor), and finally the electrical signal is recorded as data in the built-in memory and memory card. In the basic performance of digital cameras, the technical indicators such as pixel number, photographic elements, zoom ratio and lens brightness are the most critical. First, the number of pixels in the instructions and advertisements of digital cameras, the first description that catches people's attention is generally its number of pixels. The so-called number of pixels can be understood as something like a grid set on the photographic element. The color and intensity of light can be received into the camera in this grid. Therefore, the finer the grid (that is, the more pixels), the finer the particles in the photo and the better the details of the subject. However, the data marked on advertisements, samples, manuals and cameras are sometimes different. Obviously, the image file size of a 4 megapixel digital camera is only 3.9 million pixels. Is there any standard in this? Indeed, before we saw the data of these pixels, we had to think about it carefully, because the technology of image sensors developed very rapidly, and there were many loopholes in the original standard. JCIA (Japan Camera Industry Association) issued the "Guidelines for Marking Standards of Digital Cameras" in July, 20001year, which strictly standardized the names and contents of various nominal methods, in order to provide consumers with indicators that can be used as the basis for choosing digital cameras. The main point of the new standard is that, as an indicator of the performance of digital cameras, the "effective pixel number" will be given priority, and ordinary consumers should use the effective pixel number as the basis for purchasing digital cameras. The new standard is applicable to digital cameras sold from September 5438+0 to September 1 2006. JCIA hopes that this standard can become the standard of the global digital camera industry. Below we list the number of pixels that users may encounter when choosing, so that users can have a basis when judging. (1) effective pixel number is designated as the most preferred index when describing the performance of digital camera in the specification. According to the principle of physical light diffraction, after the optical path (image-taking hole) of the camera is fixed by the manufacturer, diffraction phenomenon will be formed at the outer edge when imaging on CCD, which will lead to blurred image. In order to improve the image quality, we will give up the imaging content on this part of pixels, so that the imaging units (pixels) will not be fully utilized, resulting in no actual number of pixels being provided, and most of the utilized pixels are "effective pixels". This is why we always see the "effective number of pixels" in the description of digital cameras. (2) Total number of pixels This is the specification of the image sensor itself and the number of all pixels on the sensor. When designing a series of products, the same lens and CCD may be used, but ultimately it depends on the number of pixels and the surrounding design to distinguish the grades in the market. Therefore, the imaging range of some digital camera lenses is smaller than the CCD area, and only some CCD pixels can be used. So we can often see that the effective number of pixels is less than the total number of pixels. (3) Number of recorded pixels This is the number of pixels contained in the still image finally recorded on the storage medium. Some high-resolution images generated by interpolation and intelligent pixel expansion technology can also be labeled according to this standard. Therefore, for some digital cameras with CCD with unique layout or algorithm, the number of recorded pixels represents an important aspect of their performance. Of course, the manufacturer will label the technology used to generate these pixels. (4) Output Pixels This is the number of pixels contained in the image generated by the digital camera after output conversion. This index is somewhat similar to the number of recorded pixels, but it is the resolution at which the image is finally transmitted to the computer, which is slightly different from the data in the storage medium. Do you have any good ideas after reading these indicators? It may be more intuitive to find a sample of a digital camera. In fact, there is no need to delve into their meaning. At present, the relatively new digital cameras (listed after July of 200 1 year) all take the effective number of pixels as the most obvious indicator. Under the unified standards, it is easier for us to choose products that meet our own needs. Second, the photosensitive element In addition, the size of the photosensitive element (CCD) is also very important. If the number of pixels is the same, the larger the photographic element, the larger the size of each pixel. The larger the pixel size, the more data can be processed, so that the color and intensity of subtle light can be distinguished and photos with rich layering can be generated. Mid-range digital cameras generally use 1/2.7 ~11.5 inch CCD, but some advanced SLR cameras will exceed1inch. At present, the common CCD diameters in digital cameras are: 2/3 inch and11.8 inch. If a CCD board integrates 2 million photoelectric imaging units, then we say that this digital camera is 2 million pixels. So when the size and integration of CCD board are fixed, pixel becomes an absolute concept. On the premise of the same integration level, the larger the CCD size, the higher the number of pixels of the digital camera, and of course, the greater the resolution and the more expensive it is. 3. Zoom ratio (1) The focal length of the lens is one of the most important characteristics of the camera lens. In order to make it easy for traditional photographers to understand the meaning of lens focal length of consumer digital cameras, we often convert it into the equivalent focal length of 135 camera. The focal length of a lens refers to the distance from the focal point to the lens after parallel light passes through the lens. Basically, if the position of the subject remains the same, the focal length of the lens will be proportional to the magnification of the object. That is, magnification = image size/subject size optical zoom. For example, the focal length of Nikon CoolPix 990 digital camera is 38 ~ 1 15mm (equivalent to 135 camera), so we say it is 3 times optical zoom. The original focal length of the lens is 38mm, and the maximum focal length of the lens can be adjusted to 1 15mm after the telescopic change of the lens system. At the same shooting distance, the subject can be enlarged by 3 times. (2) Digital Zoom Today's digital camera has evolved into a small computer with an operating system that can execute established programs. Through the calculation of the program and the cooperation of the optical system, the object can be enlarged locally, and the effect of optical zoom can be simulated by interpolation. Digital zoom will inevitably lose the image quality. Under normal shooting conditions, we do not recommend using the digital zoom function. But we also know that "poor photos" are better than "no photos". In some special cases, we will still use the "digital zoom" function. (3) Optical Zoom VS Digital Zoom The image quality of optical zoom is better than that of digital zoom. Please try to use the optical zoom function. Optical zoom and digital zoom are calculated as follows. If the optical zoom of a camera is 3X and the digital zoom is 4X, the camera can achieve a magnification of 12X by combining the optical zoom and digital zoom functions (although this is not practical). (4) Fixed focus and zoom No matter what brand of camera, the zoom function will still cause the loss of image quality. Therefore, in the digital camera/lens system of the same level, the result of fixed-focus lens should be sharper than that of zoom lens. On the other hand, the fixed-focus lens is easier to design and lower in cost, but it is not as convenient as the zoom lens in composition. For digital cameras, the larger the zoom ratio, the more convenient it is to take a long view. But correspondingly, the bigger the lens, the higher the price. If you only use a digital camera for recording, and the products you use are as light as possible, you can choose products without zoom function. If you need a little zoom function, a zoom function of about 3 times is enough. However, "optical zoom ratio" and "digital zoom ratio" may appear in the manual. Among them, the performance of the lens is "optical zoom". "Digital zoom" refers to the function of cutting out some images and enlarging them. So the more you zoom in with digital zoom, the worse the picture quality. Fourth, the lens brightness "F value" indicates the lens brightness. When shooting without flash at noon, it is enough to reach F4.5 or so, but it is best to reach F3.5 or F2.8 when shooting at night or in a dimly lit room. Even so, the performance of the lens cannot be judged by the specifications alone. There are no data such as ambiguity, color representation, external light quantity and aberration in the manual. In addition, photography purposes and personal interests are different, and preferences are also different. In this regard, it is best to refer to the test report published in the magazine. 5. Other specifications that have a great influence on the usability of digital cameras include the starting time from turning on the power supply to shooting, the shortest time for continuous shooting, and the time difference from pressing the shutter to closing the shutter. In order not to miss any shooting opportunity, it is obvious that the smaller the values of these indicators, the better. Resources: /viewthread.php? tid=97 17