Information about digital cameras

1. Pixels and resolution pixels are the most basic units of digital images, and each pixel is a small point, and when pixels of different colors are gathered together, they become a moving photo. Digital cameras often use pixels as the basis for classification, but many people think that the number of pixels is the number of photosensitive points on CCD photosensitive units. In fact, this statement is not completely correct. At present, many manufacturers have adopted special technology. Digital photos with higher resolution can be generated under the CCD photosensitive unit with the same photosensitive point, such as Fuji's SuperCCD and Epson's HyPic technology. What is the relationship between pixels and resolution? How to interpret these two figures when purchasing?

★ The higher the resolution of a picture, the more pixels are needed. For example, a picture with a resolution of 64×48 needs about 31, pixels, and a picture with a resolution of 284×1536 needs up to 3.14 million pixels.

★ The resolution can have multiple values. The more resolutions provided by the camera, the higher the flexibility of taking and saving pictures.

★ The resolution of a picture is related to the imaging size and magnification ratio at the time of output. The higher the resolution, the larger the imaging size and the higher the magnification ratio.

the total number of pixels refers to the total number of pixels contained in the CCD. However, due to the lack of light on the edge of CCD, some of them are not needed for shooting. Subtracting this part of pixels from the total number of pixels is the effective number of pixels. Therefore, when reading the product manual, remember to pay attention to the effective number of pixels that can be used for actual shooting, not the total number of pixels.

2. The quality of the lens and shutter lens directly affects the quality of the camera. Under normal circumstances, manufacturers with deep background of traditional cameras will have better lenses of their digital cameras.

★ Focal length Due to the special lens specifications of digital cameras, it is impossible to predict the range of scenes that can be photographed from this data, and most manufacturers will increase the focal length value equivalent to 35mm of traditional cameras after the lens focal length parameters. If it is a souvenir or a life photo, you only need to buy a fixed-focus lens model. If there are diversified needs, a camera with three or more optical zoom capabilities will be more suitable. Focal length, also called focal length, usually refers to the distance from the center point on the lens axis to when the image can be clearly imaged. In a camera, it refers to the focal length of the whole lens group, in mm (millimeter). The longer the focal length, the narrower the angle of the visual range of the lens, but it has the effect of magnification and proximity, just like the lens of a telescope; The shorter the focal length, the larger the shooting range and the smaller the relative object, which is suitable for shooting large scenes at close range, which is what we often call a wide-angle lens. For digital cameras, the longer the focal length, the longer the depth of the lens group. In addition, data such as f=5.5mm or 5.5mm can be found from the camera lens. However, because the focal length of the lens of digital cameras is generally much shorter than that of ordinary 35mm cameras, manufacturers will often indicate something similar in the instructions: 36mm lens equivalent to a 35 mm camera for users to compare.

★ Aperture range The larger the aperture is, the more it can adapt to insufficient light. If there are more than two aperture values, the application flexibility of the camera will be greater. Aperture is one of the important mechanisms affecting exposure, which usually refers to the control device composed of about 5 to 9 metal sheets in the lens group, which can form circles with different sizes to control the amount of light entering the lens. The larger the aperture, the more light enters per unit time. The size of the aperture is expressed in numbers, and the larger the number, the smaller the aperture, that is, the less light enters. The marks on the lens refer to the maximum aperture of the lens, that is, the value in the fully open state, for example, 1: 3.2, but on the zoom lens, you will see the marks of 9.2-28 mm1: 2.8-3.9, indicating that the maximum aperture is F2.8 when the focal length is 9.2mm, and F3.9 when the focal length is 28 mm..

★ Shutter digital camera shutter can support 2 ~ 1/1 seconds, which can meet the general requirements. Of course, if the shutter range is wider, it can meet all kinds of strict shooting conditions, such as shooting high-speed moving objects or starry nights. The shutter is used to adjust the exposure time of the camera. The unit is seconds, and it is expressed in reciprocal. For example, 3 and 25 mean 1/3 second and 1/25 second, so the smaller the number, the slower the shutter speed. The faster the shutter speed, the easier it is to capture high-speed moving images. Generally, it is not easy to blur the images due to shaking when shooting, but the high speed may lead to insufficient light input. Usually, the high-speed shutter must be used when the light is strong, or the aperture should be enlarged. When the light is insufficient, a slow shutter is more suitable, but a tripod may be needed for assistance.

3. Macro shooting Macro is to zoom in and zoom in on the subject to be shot. The key point is to shoot tiny objects to the size you want. In macro mode, various digital cameras have different abilities, and some can even be close to about .1 cm to take close shots.

4. Other functions, such as red-eye flashing, white balance and exposure compensation, are more flexible for shooting in various environments.

★ The photosensitive part of automatic white balance correction digital camera is equivalent to the negative film of traditional camera, and the photosensitive element of digital camera is fixed, so it is necessary to reflect the changes of light source with the help of white balance correction ability. It is mainly designed for the light sensitivity in different environments. Different light sources will produce different degrees of color deviation, which may make the color blue and yellow, and white balance correction can correct it.

★ exposure compensation because the automatic exposure function of the camera takes the amount of light reflected by medium gray as the comparison standard, if there is too much white (too much reflected light) in the shooting picture, the amount of light will be higher than the photometric standard value, so the camera will be misled into thinking that the light is very strong and the aperture will be reduced, resulting in underexposure of the photo and the white part will become not white enough. The exposure compensation is aimed at this situation, and the exposure is increased by 1 or 2 squares to have a bright and correct image. On the other hand, in most cases of black, it is necessary to reduce the exposure by 1 or 2 squares.

many consumers, because they don't know about digital cameras, unilaterally think that high pixels are good. Not really. When purchasing a digital camera, we should give consideration to its digital characteristics and optical characteristics.

1. The lens of a digital camera. A well-designed high-end camera lens is composed of multiple groups of lenses and contains aspherical lenses, which can significantly reduce color shift and minimize graphic distortion and distortion. The expensive fluorite or glass is used as the lens. In order to reduce the weight and cost, the lenses of household and semi-professional cameras are made of resin.

2. Image value of CCD of digital camera. CCD is the heart of digital camera, and it is also one of the main factors that affect the manufacturing cost of digital camera. Therefore, it has become an important standard for classifying digital cameras. At present, the entry-level products are 3-5 million pixels, while commercial and semi-professional users prefer products with more than 5-1 million pixels.

3. Zoom of digital camera. Optical zoom is a real zoom, which will not affect the imaging quality of photos; Digital zoom is electronic zoom, which is a local enlargement at the expense of photo clarity.

4. Battery and power consumption of digital camera. Digital cameras have LCD display and built-in flash, so the battery consumption is larger than that of traditional cameras. Using the No.5 battery is cheap and can be bought anytime and anywhere, but it won't take long for the battery to die. Therefore, it is best to choose a model equipped with rechargeable lithium batteries. At present, mainstream digital products have been designed as lithium batteries, and complete charging equipment is provided as accessories.

5. Additional functions. The more functions there are, the more fun and versatile it means to use digital cameras. For example, many digital cameras have video output function, which can be connected to TV to browse photos; Some can set their own startup pictures and shutter sounds like mobile phones; Some can have short-term digital video recording function. The installation of the driver of digital camera should be very simple, and it should be able to download pictures quickly and have photo previews. For example, the software function attached to Canon digital camera is perfect, which can classify and manage pictures, and the settings when printing are more varied, and pictures can also be simply modified.

The image sensor is the decisive factor of the camera performance. In general, the pixel value of the image sensor should be greater than the maximum pixel value of the real shot image. Some manufacturers use software interpolation to increase the pixel value of the image in order to make up for the pixel shortage of the image sensor. In fact, this interpolation method can be realized in almost all image processing software, so it is of little practical significance. The purchase must be based on the hardware pixel value of the image sensor rather than the maximum pixel value of the output image.

digital cameras record photographic information in a semiconductor element called CCD (Charge Coupled Device), not on the film of a silver salt camera. The CCD size, like the TV set, refers to the diagonal length, expressed in inches, such as "1.27 inches (note)". The larger the CCD, the more pixels and the higher the sensitivity. Therefore, with the same number of pixels, the larger the CCD, the better the image quality. CCD size 1/2.7 inch (4.mm×5.3mm)1/2 inch (4.8mm×6.4mm)1/1.8 inch (5.19mm×6.91mm)2/3 inch (6.6mm×8.8mm) Note: 1 inch is equal to 2.54cm, and the CCD of digital camera is adopted.

Second, the four basic principles of purchasing a machine

● For ordinary home users, if they are limited to family entertainment and pay great attention to practicality, powerful functions and high cost performance brought by durability are the first choice factors. At present, the 3-megapixel and 5-megapixel models that dominate the market can meet the imaging requirements. Multiple shooting modes, wide ISO value setting range and high-speed and accurate focusing are necessary functional features, and the metal casing that ensures durability is also an essential consideration.

● For those consumers who pursue fashion avant-garde, the close combination of shape design and highlight function is the first choice standard. Small shape, bright colors and comfortable hand feel are essential, and some highlight functions, such as macro shooting, are the icing on the cake for this kind of products.

● if you are a professional-level user, the most important thing is the ultimate pursuit of imaging quality. Manual operation function is necessary. Replaceable lens, CMOS image sensor with more than 6 million pixels and various image recording modes are the guarantee of high image quality. If we have an explosive price of less than 1, yuan, more professional photographers will flock to it.

● The last thing to consider is where to buy. A regular digital camera sales counter will ensure that your camera is "born". Brand effect should be considered when purchasing, because it is the main guarantee for the overall quality and after-sales service of digital cameras.

Third, the preparatory steps for buying a camera

Step 1: Define the purpose and purpose of buying a camera

It is very important to determine the purpose and purpose of buying a camera. Only by knowing our own needs can we choose to buy the machine we really need through mergers and acquisitions. Otherwise, it is possible to spend a lot of money on the camera, and it turns out that the functions can't meet your own requirements, or there are too many functions to use at all. We can think about what we bought a digital camera for. For example, some friends buy digital cameras to travel; Some friends hope to learn photography; Some friends want to take macro photos; Of course, some people want to take close-up photos of people or take pictures of their newborn children as souvenirs. In short, we must clearly consume.

The issue of photo output also needs to be considered in advance, and whether you need to develop large photos or just watch them on the screen. Through this consideration, we can decide how many pixels we need to buy a machine. If we just look at it on the screen, then a machine with 3 million pixels is enough. If we want to print, and print to more than 1 inches, then we need to buy a camera with as high a pixel as possible.

Step 2: Decide the psychological price

After deciding the purpose and purpose of buying a camera, we should decide an affordable psychological price according to our economic ability, such as 3 ~ 4 yuan or 6 ~ 7 yuan. This can help us save a lot of time and be more purposeful when choosing. DC is still a luxury, so everyone must do what they can. It is meaningless to compare with others, just enough.

Step 3: Collect data through various channels

It is very important to collect data in the early stage, so that we can have a certain understanding of the machine to be purchased. There are many ways to collect product information. First of all, many manufacturers will have certain publicity pictorials when they launch digital cameras. We can go to the vendors to have a look. Secondly, media advertising is also a very important way. There are many digital camera advertisements in IT newspapers today, so we should pay attention to them. Thirdly, now many digital magazines or some newspapers will have a certain space to introduce or evaluate digital cameras, and we can also buy some to read.

if possible, you can download the manual of the corresponding camera and have a look. This is very good for buying machines: on the one hand, it can make you more familiar with the machines, on the other hand, it can make you prepared for the basic operation when you buy them. I like reading instructions very much myself.

technical data can help us understand the appearance, functions and other information of digital cameras. And we should look at the actual photos. In this way, you can know the characteristics of DC you are concerned about, such as color, image quality and so on. We can go to the digital photography website to learn about this.

step 4: roughly determine the model

it is very important to collect product data, which can let us fully understand the characteristics of digital cameras. But just looking at these materials, we can only have a perceptual understanding. Only by actually looking at the machine or even trying it out can we have a rational understanding of the machine. This requires us to go to the mall. We can look at the prototype in the window or counter. The real machine may look different from the one in the photo, or it may look better. We can also watch other people buy machines and listen to what others say. Of course, we can also let the merchants take out the machine, actually touch it and operate it. Depending on the machine, you should also ask about the price. When asking about the price, you should pay attention to the fact that the quotation of the merchant usually leaves room for counter-offer. Also, ask whether the price they quoted is licensed or parallel.

Step 5: Choose the right time to buy

After deciding on the machine to buy, you should choose "auspicious day" to buy DC back. When I say "auspicious day", I actually want to seize the opportunity by myself. The price of digital products changes rapidly, so it is very important to judge the market. However, it is clear that you should avoid buying before the festival as much as possible. There must be a lot of people buying machines before the festival, and the price will not be cheap.

Must-read when buying a camera

When buying a camera, we 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 the money first, but after the inspection.