1. LCD screen
The LCD screen is a small window for preselecting future scenes and browsing photos, which embodies the greatest superiority of digital cameras over traditional cameras. Some manufacturers are ingenious in the design of LCD screens, such as Pentax 330GS, whose LCD screen can be flipped 180, so that photographers can fully appreciate the fun of taking selfies. The LCD screen is usually a TFT color LCD screen with sizes ranging from 1.5 to 1.8 inches. Generally speaking, the bigger the LCD screen, the better, but don't neglect its clarity in pursuit of a big screen. The bigger the screen, the more power it consumes. The clarity of LCD is related to the number of pixels, ranging from tens of thousands to hundreds of thousands. Olympus μ300 has done a good job in this respect. Special emphasis should be placed on whether there are bad pixels on the LCD screen. Some bad pixels are not visible at all in normal light. When selecting, you can cover the light with paper or clothes, and carefully observe whether there are abnormal bright spots on the LCD screen from all directions.
The LCD screen is the first item that needs to be focused on.
2.CCD effect
CCD: Charge Coupled Device (CCD), a special semiconductor device, has many identical photosensitive elements on it, and each photosensitive element corresponds to one pixel, so the number of pixels in a digital camera is also the number of photosensitive elements on the CCD. If the photosensitive element is broken, every photo taken by this machine will leave a bad spot, which is a very serious problem. The method of identification is to take a group of "black" photos in a dark environment or in front of dark objects (of course, if you are careful, you should also test other modes, such as images taken at night), and input the photos into the computer to enlarge and look carefully. If suspicious white or red spots are found, check whether other photos have such spots in the same position. If so, that means never buy a machine if there is a problem. If you don't want every photo to have one or several "logo" points, you must make great efforts in this step. In addition, different cameras have different shooting effects due to different lenses, processing methods and sensitivity. Be sure to test the effects of various modes (such as automatic, manual, distant view, close view, night view, etc.) when purchasing. ), and it is best to send the photos to the computer to see if their colors are true and how delicate they are. For example, when taking close-ups, we can compare the fineness by clapping patterns, cell phone textures, faces and so on.
3. Lens and focal length
The quality of the lens directly affects the shooting effect. Good camera lenses are generally made by well-known brand manufacturers, such as Schneider and Pentax. The lens consists of a series of lenses. Pay attention to the smoothness of the lens, whether there are scratches on the surface and whether there is dust on the inner lens when buying. In the long run, we should also pay attention to whether the design of the fuselage protects the lens well.
The focal length reflects the distance at which the scene can be photographed. Zoom can be divided into optical zoom and digital zoom. The zoom formula of digital camera is: zoom = optical zoom × digital zoom. Optical zoom relies on the structure of the lens to achieve zoom. The larger the optical zoom factor, the farther the object can be photographed. Digital zoom enlarges a part of the pixels on the original CCD sensor to the whole picture, and the image is enlarged at the expense of clarity, so the amplification effect is not very "real". Some cameras promote high-magnification zoom, so buyers still need to find out what optical zoom and digital zoom are, because digital zoom does not need to be blindly pursued.
Don't underestimate the battery. Plenty of electricity will make it much easier for you to use.
Macro refers to the closest shooting distance of a wide-angle lens, which is very practical when shooting still life and flowers. Of course, the smaller the macro, the better. The macro of Canon A70 camera is excellent, only 5cm.
4. Function
Friends who like special effects should pay attention to this item. Different brands of digital cameras provide obviously different functional modes. Generally, we are more concerned about whether to support continuous shooting; Whether recording short films is limited by time or memory card and whether there is recording function; LCD menu is Chinese or English, manual focus point, several white balances, etc. If you have special requirements, you should care about what special effects the camera provides.
5. Battery
There are many kinds of batteries for digital cameras, but there are two commonly used ones: special lithium batteries and No.5 AA batteries. For the special lithium battery, it can be judged whether it is new or used by checking whether the metal interface of the battery is scratched. In addition, users generally need to buy another spare part. The original special lithium battery is more expensive, generally more than 200 yuan or about 300 yuan, 1000mA, and can take more than 200 photos continuously. In contrast, the No.5 AA battery is much more practical. The most noteworthy is Samsung's V3, which is actually compatible with nine different batteries, such as CR-V3 and AA batteries. Its design is unique.
6. Storage Plug-ins
General digital cameras have built-in memory. But it may not be enough. Users have to buy another memory card, usually 128MB or 256MB. There are many kinds of memory cards, CF, XD, SD, MMC and memory stick. These memory cards are not universal. Each digital camera is equipped with one or two memory cards. For example, Kodak 4330, Canon A70 and Pentax 330RS use CF cards, while Casio R3 uses SD cards. Different cards have different storage speeds and different prices. XD cards are faster, and support for continuous shooting is stronger, while CF cards and memory sticks are the slowest.
There are many kinds of memory cards, so pay attention to the compatibility with other devices when choosing them.
7. fuselage design
Lightweight and metal fuselage are more popular now. Beautiful and fashionable appearance is naturally favored by people, but practicality should be considered, mainly focusing on the accuracy of the fuselage and the rationality of the design, as well as whether it can be well dustproof and waterproof. Of course, the thinner the camera, the harder it is to hold, and these factors cannot be ignored.
8. Configure accessories
In addition to special batteries and built-in memory cards, traditional digital camera accessories also include manuals, software CDs, chargers, USB cables, wristbands and so on. Be sure to check whether it is complete one by one according to the instructions when buying. Some cameras give away some accessories. For example, some models of Pentax and Samsung have their own remote controls for taking selfies. The seller may refuse to give it because it is out of stock, and the buyer must ask for it before paying, otherwise the accessories may be out of stock all the time. In addition, users can consider buying camera accessories such as tripods to facilitate shooting.
9. Service Commitment
The replacement cycle of licensed digital cameras is generally from 15 to 1 month, and the warranty period is generally one year. When buying, you should also remember to ask about the conditions and methods of replacement and maintenance, whether there is a national warranty, and what to do if the product stops production during the replacement period. Especially during the replacement period, buyers should take pains to test the camera in all directions to find out its shortcomings. When problems are found, they should confidently find the seller to replace it, but the seller will often be very tricky and prevaricate with reasons such as out of stock or delayed replacement. At this time, the buyer will lose his temper or respond with "protracted war" tactics, so that he has to replace it for you.
In addition:
When buying a camera, you need to check it carefully to avoid buying defective products or being cheated by JS (profiteer). Here we give a detailed inspection step, as long as you follow the following instructions, there will be no problem:
1. Never pay JS first, and then pay after inspection;
2. See if the packaging is old. If so, it may be replaced by others, or a product that JS has stored for a long time;
3. After unpacking, check whether the accessories in the box have been used or obviously disassembled; Pay special attention to whether there are scratches on the battery pins;
4. Check the appearance of the machine. Look for scratches on the fuselage, including lens, LCD, EVF and shell.
5. Try to shoot, and zoom to see if you can shoot clearly. If you are not familiar with the machine you are going to buy, you can shoot it with an automatic file when you try it out. In addition, the flash has to be tried;
6. Then take a closer look at the LCD and EVF. You can block the lens a little with your hand, so that you can see a solid color image, or face the black and white paper.
7.CCD is the key component of DC. If there are bad spots on it, it will affect shooting. Because it is difficult to see the bad points of CCD directly on DC, it is necessary to import the picture into PC and watch it again. If there is no computer in the business, it is recommended to talk with the business about a certain replacement cycle, and then go home and feel at ease to test;
How to test bad points
Before we discuss how to test bad points, we need to explain what bad points are. Simply put, it is a point on the CCD that will never be sensitive, or this point will always be on. Usually always at the top, rarely not. So why is there a bad point? This is related to the manufacture of CCD. Although the technology is very developed now, it still can't guarantee the high output of CCD. Just like LCD, it may be defective. So we need to test the machine after we buy it.
The test of bad points is actually relatively simple. We can test it in two ways: one is to look at the original picture with our eyes. In fact, this method is more intuitive, but be careful, otherwise it is easy to miss points. The second is to test with software. The most popular bad point testing software is DEADPIXEL. Usually, if there is a computer in the place where DC is sold, this software can be bought there.
Before the test, we should take some all-black photos first. Ordinary photos can't be tested. This is very important. For the machine with lens cover, we only need to cover the lens cover to shoot. If there is no lens cover, such as Casio, then we can put a thick piece of paper on the flat panel, put down the DC lens and buckle the lens on the paper to shoot. It should be noted that the light must not enter the lens, and at the same time, don't use too much force, which will easily damage the machine.
The shooting parameters can be set to the maximum aperture and ISO 100. As for the shutter, we need to choose 1/60 and the slowest shutter. That is, take a photo with different shutter speeds.
After shooting, we can import the photos into the computer and open DEADPIXEL for testing. After opening this software, we can see the interface as shown below. We click the "Browse" button and select the photos that need to be tested. Then we press the test button and the results will appear. If the photo of 1/60 is more noisy than 10, try to change it, otherwise it may affect the shooting.
Check that all accessories are there. Usually there is a list in the box, which explains in detail how many accessories are included, and we can compare them.
Precautions for computer use
1, CPU: At present, the mainstream processor of notebook computers is P4, which has good performance and better speed. For users who need to install more complex application software, even if the price is high, it is worth considering; At present, many manufacturers use P4 processor of desktop instead of P4-M in order to reduce costs. The notebook with P3 processor is in the inventory clearing stage, and its price is low enough to handle ordinary documents and edit reports. In addition, Celeron processors are cheaper in the low-end market.
2. Display screen: LCD is the most expensive part of notebook computer. The mainstream screen size is 14. 1 inch, and there are also 15 inch. If users travel frequently, it is recommended to choose some ultra-thin and ultra-light notebooks with screen size of 12 inch ~ 13 inch. If the user is sitting in an office, he might as well choose a bigger one, which looks more comfortable.
3. Memory: Although 128MB is enough, it will be easier to run WinXP if it is increased to 256MB. At present, the mainstream of memory is DDR.
4. Hard disk capacity: At present, the capacity of notebooks is basically above 10GB, while mainstream models are equipped with 20GB or 30GB. But if you have multimedia files to store, you should choose a hard disk with as large a capacity as possible.
5. Floppy drive: The laptop floppy drive is completely built into the computer; However, in some ultra-thin models, there is no floppy drive or external connection. It is best to choose USB interface, plug and play, and don't connect when not in use, which saves space and does not affect the use.
6, optical drive: DVD-ROM is popular at present, and even CD-RW (recordable) is added. From the point of view of use and economy, CD-ROM is enough. Pay attention to the stability, sound, error correction ability and speed of the CD-ROM drive.
7. Battery and power adapter: Try to buy lithium batteries. For the ACAdapter, it should be noted that if the working time is long and the temperature is too high, an exception will occur.
8. Network function: Recently, all new laptops have listed network function as standard: including 56K modem and 10/ 100M Ethernet card. If it is optional, it is recommended to install it, because the modem is still very convenient for notebook computers, and the network card can easily connect to the local area network or the Internet.
9. Extensibility: We should fully consider the expandability and upgradeability of products. The most commonly used USB interfaces, many of which are easy to use, can easily connect digital cameras, scanners, mice and other peripherals.
10. Is the operating system pre-installed? If there is no pre-installed operating system, it is called "bare metal". This has certain influence on the stability of the system.
Three mobile phone precautions
Buying a mobile phone should be considered from the following aspects. First, the price; Second brand; Third, quality; Fourth, after-sales service and warranty. Among them, brand and quality are the most important. It is generally recommended that you choose branded mobile phones and buy them from reputable businesses.