Sony digital camera ccd camera all functions are normal, and there is no photographic image on the unique screen.

1, get out of the misunderstanding of high pixels

As one of the standards to measure the quality of digital cameras, pixels are often regarded as the focus of investigation when consumers buy digital cameras. Therefore, many consumers have gone into the misunderstanding of high pixels, blindly pursuing high pixels and taking pixels as the only standard to measure the quality of digital cameras. Digital cameras use CCD or CMOS to sense light, and the number of pixels for shooting images depends on the number of photosensitive units on the CCD or CMOS chip in the camera. Theoretically, the more photosensitive units there are, the clearer the image will be. However, because the photosensitive element area of digital camera is much smaller than that of traditional film, adding too many photosensitive units on the limited chip area will cause many problems, such as the reduction of image signal-to-noise ratio and sensitivity.

As we all know, digital cameras need to rely on the internal image processing engine to reduce color errors. The imaging principle of digital camera is essentially different from that of traditional camera. The data obtained by photosensitive elements must be processed and combined to generate the final image file, and the calculation method of processing engine directly affects the quality of the final image. Therefore, pixels can indeed be used as one of the important standards to judge the level of digital cameras, but it is not the only standard. It is necessary to comprehensively examine the quality of digital cameras through their comprehensive indicators.

2. Importance of the size of photosensitive element

There are many factors that affect the imaging quality of digital cameras, among which the size of the photosensitive element of digital cameras has a great influence on imaging. The larger the size of the photosensitive unit, the more sensitive the photosensitive element is to light, the smaller the signal noise generated, the better the reproduction of highlights and shadows, and the higher the contrast. However, if too many photosensitive cells are added to the limited photosensitive element area, the photosensitive cells will be too small, which will lead to the problems of image signal-to-noise ratio and sensitivity reduction.

The number of pixels of the image taken by a digital camera is equal to the number of photosensitive units on the CCD photosensitive element in the camera. Therefore, if the number of pixels is the same, the individual size of the photosensitive unit with large photosensitive element size used in digital cameras is naturally larger.

3. Selection of 3.CCD and CMOS

Different from the traditional camera, which uses the photographic principle of film to store images, the digital camera uses photographic elements to convert the light shining on the chip through the lens into charges, then processes the electrical signals into digital signals, and then the image processing engine compresses the digital signals into a certain format and stores them in the cache to generate digital photos. Among them, the importance of photosensitive elements is self-evident. At present, there are two kinds of photosensitive elements used in digital cameras on the market, CCD and CMOS, which are quite different in function and performance. Because CMOS technology is not very mature when digital cameras are popularized, most consumers think that CCD is better than CMOS, and CMOS photosensitive elements are only suitable for mobile phones or other occasions with low image requirements.

In fact, this is a wrong understanding. In fact, the photosensitive element used by most digital cameras is CCD. This special semiconductor material can convert light into charge through the photosensitive element on the surface, and can produce low noise and high performance imaging, so it has been widely recognized and applied. But in fact, CMOS photosensitive elements also have many advantages. CMOS converts light through semiconductors, but unlike CCD, each photosensitive element of CMOS has an amplifier, which can convert charge into electrical signals. CMOS can amplify signals pixel by pixel. This method can save any invalid transmission operation, so it only needs a small amount of energy consumption and reduces the noise. The imaging effect of well-made CMOS sensor is not worse than that of traditional CCD. Therefore, it is not possible to measure the quality by using CCD or CMOS sensors in digital cameras. The quality of a CMOS sensor depends only on the quality and maturity of technology. The CMOS digital camera EOS 10D made by Canon is a quasi-professional digital camera.

4. The importance of the lens

It can be said that the lens is the soul of the camera, and digital cameras are no exception. Whether it is an optical camera or a digital camera, the lens is one of the most important elements.

On the surface, digital cameras have low requirements on the optical resolution of the lens due to the limited resolution of the photosensitive elements. However, because ordinary digital cameras use CCD or CMOS photosensitive elements, their area is much smaller than that of traditional film, so the requirements for lens resolution are more stringent. Otherwise, even if the number of pixels in a digital camera is high, the imaging quality will still be poor due to the lens. In other words, the resolution of optical lens used in digital camera must be better than that of photosensitive element.

In fact, the complexity of digital camera lens structure and the requirements for manufacturing technology are not lower than those of traditional cameras. It is mainly composed of multiple groups of lenses. The higher the imaging quality, the more lenses. It's hard to say which lens is the best, but large aperture, multiple lenses and multiple groups, including aspherical lenses and high-quality coated lenses, are the best choices for users who require perfect image quality.

In addition, the lens materials of digital cameras are divided into glass and plastic. Some manufacturers emphasize that their camera lens is made of glass, so it has good transparency and the projected image is clearer. But in fact, glass lenses may not bring clearer images than plastic lenses, and glass lenses may also increase the weight of the camera, so we should consider it from many aspects when purchasing, and we should not be limited to this.

5, pay attention to the details of the zoom function

When purchasing digital cameras, the zoom factor is the focus of consumers' general concern. A larger zoom factor can make a digital camera more flexible, but it is not easy to know the shooting situation of a digital camera just by looking at the size. Zoom is divided into optical zoom and digital zoom. First of all, pay special attention to the range of optical zoom. The smaller the minimum focal length of the camera, the larger the wide-angle shooting range, which is beneficial to shooting large scenes, while the larger the maximum focal length, the stronger the telephoto ability. Lenses with focal lengths from 38 mm to 1 14 mm and 35 mm to 105 mm are all triple zoom lenses, but obviously, lenses with focal lengths from 38 mm to 1 14 mm lose the ability to shoot large scenes, while those with focal lengths from 35 mm to/kloc-0.

In addition, unlike traditional cameras, digital cameras also provide digital zoom function, which is very different from optical zoom. Digital zoom is to enlarge the photo taken and then fill in the blank scientifically, which is called interpolation amplification. It should be noted that the more interpolation components, the more details of the sacrificed picture, and the lower the definition. Therefore, the general digital zoom does not have much practical significance. Therefore, when purchasing digital cameras, we should focus on the optical zoom range. Don't listen to the irresponsible propaganda of the merchants, and mistakenly think that the digital zoom function can make up for the lack of optical zoom range.

Matters needing attention

1, first look at the fuselage: first look at whether there are fingerprints on the fuselage, if there are, it means it is not a new machine, or even a prototype or rework machine.

Shake it gently before buying and listen to the sound of loose parts. If there is, it must be a quality problem. No matter what the profiteers are quibbling about, replace them immediately;

Step 2 check the viewfinder

Pay close attention to whether there is any deviation between the scene taken and the scene seen by the viewfinder. If there is, it may be that the pentaprism inside is crooked, or the photosensitive element is crooked, which is definitely a quality problem. Replace immediately;

3. Detection time setting

For a brand-new digital SLR, the first opportunity requires you to enter the current time. If the time in the newly opened digital SLR has been set, it means that this digital SLR has been used.

4. Check the LCD screen

The way to check whether there are bright spots or dark spots on the LCD screen is exactly the same as when buying a laptop or LCD monitor: cover the lens and take a full black picture, and then take a full white picture against a piece of white paper, so that you can observe whether there are bright spots or dark spots on the LCD screen with the naked eye.

Step 5 check the picture number

Digital SLR can also be selected by photo number. However, it should be noted that a completely blank memory card must be used, otherwise, the initial number of the file will be disturbed.

6. Detect the bad point of the photoreceptor

The bad point of photosensitive element is detected by DeadPixelTest software. The ideal state is that there are no bad spots and noises. Of course, a little noise is totally acceptable.

Step 7 check the lens

The original unopened lenses are spotless. See if there are any useful marks on the lens bayonet and dust on the mirror.

8. Check the completeness of the attachment according to the instructions.

Generally speaking, a digital SLR includes host, battery, charger, power cord, USB cable, shoulder strap, optical drive, manual, warranty card and other accessories (digital SLR is not sold without memory card). If it is a machine, a lens will be added. It should be noted here that some digital SLR are likely to have several sets of lenses to choose from when they are sold. So when buying a machine, you must pay attention to the inspection of the lens.