Terminology of digital camera

DV: digital camera.

The most critical part of DC: CCD, is the photosensitive original. Its basic size determines the resolution of the camera.

First, the definition of digital camera:

1. Digital camera is a kind of camera that uses electronic sensors to convert optical images into electronic data. Different from the principle that ordinary cameras record images on film through silver bromide's chemical changes, the sensor of digital cameras is light-sensitive-{ZH-CN: Charge Coupled Device; Zh-tw: Charge Coupled Device }-(CCD) or Complementary Metal Oxide Semiconductor (CMOS).

2. Use electronic image sensor instead of film camera, instead of taking photos with film.

Second, you need to know the parameters when buying a digital camera.

Image sensor

Image sensor is usually a charge-coupled device (CCD, similar to that used in cameras), which is the core of digital cameras. The pixel number of the sensor used by the camera is not the only factor that affects the photo quality, but it is the main factor. A high-pixel camera can produce the clearest image, the truest color and the truest skin color. Some digital cameras use CMOS (complementary metal oxide semiconductor) sensors to reduce costs, but this will make the captured images dark and not fine enough.

Image sensors are divided into CCD (Charge Coupled Device) and CMOS (Complementary Metal Oxide Semiconductor). The main argument in favor of CCD chip is that this chip is more sensitive than CMOS, so it can take better photos in dim light. Photographs taken by cameras using CCD chips are also clearer than those taken by CMOS, and sometimes there is a "noise" problem when using COMS chips-the images have some shortcomings.

On the other hand, the cost of CMOS chip is lower, and the cost saved here can be translated into lower camera price. In addition, CMOS chips absorb less energy than CCD chips, so cameras with CMOS chips can last longer when changing batteries.

In order to ensure the image quality, most digital cameras adopt CCD technology at present.

camera lens

A good digital camera doesn't just rely on resolution to improve quality. Whether what you see can be well transmitted to the image sensor for recording depends on its lens.

focal distance

In traditional cameras, the focal length refers to the distance between the center point of the lens and the photosensitive film. On a digital camera, the focal length is the distance from the center of the lens to the image sensor. We will find that the nominal focal length of digital camera lens is much smaller than that of traditional camera. For example, the focal length of Nikon COOLPIX995 camera is 8-32mm. This is because the focal length of the lens in digital camera design is actually much shorter than that of the traditional 35mm film camera. Usually, the focal length mentioned in the data or instructions of digital cameras is equivalent to that of traditional cameras. For example, the focal length of Nikon COOLPIX995 camera is equivalent to the focal length of traditional camera 38-115 mm.

Optical zoom lens helps you to change the focal length conveniently, enlarge and highlight the required image details, and omit unnecessary background, which of course increases the cost of the camera. At present, most high-end digital cameras use 2-3 times optical zoom lenses, and some lenses also use aspherical lenses, which effectively reduce aberration and dispersion.

Triple zoom lens is enough for most people, but if you want to have more flexibility or get some special effects when using the lens, you should choose a camera with lens accessories, such as Nikon's digital camera, which provides extended range, wide angle and fisheye lens.

If the zoom lens is important to you, make sure that the digital camera you buy is optical zoom instead of digital zoom. Optical zoom is a real zoom lens. Digital zoom only refers to the image processing process inside the camera. At that time, when digital zoom was used, the camera would enlarge the middle part of the picture and cut off the four peripheral edges. The result is the same as opening an image in image processing software, cutting off the periphery of the photo, and then enlarging the rest. Enlarging the zoom area will reduce the resolution and quality of the image.

concentrate

Some digital cameras have fixed focal length lenses, which means that the focal length cannot be changed. Usually, this kind of lens makes the image clearly visible from a few feet in front of the camera to infinity. Many cameras have manual focusing function, which allows users to adjust the focal length to three different distances. Among these settings, there are macro mode for shooting in a particularly close range, portrait mode for shooting objects more than ten feet away from the camera, and landscape mode for shooting distant objects. One of the advantages of a digital camera lens with very short focal length is that it has a very large depth of field. This means that the area of sharp focus (that is, fixed focus camera) is much larger than that of typical film camera.

Different cameras provide different focus ranges, which may be the most important for close-up photography. If you want to take a lot of close shots, you must compare the minimum distance between the camera and the subject. A camera with autofocus function can automatically adjust the focal length according to the distance between the subject and the lens. Most cameras with auto-focus function provide a very useful function called focus lock. With this function, you can accurately point out which object you want the camera to focus on clearly, no matter where it is in the picture. Usually you aim the center of the viewfinder at the object first, press the half shutter button to lock the focus, then move the viewfinder to make a composition and take a photo.

Some high-end digital cameras enable you to set the focus at a specific distance from the camera. Sometimes this function is very useful, because the autofocus mechanism may not always focus well when shooting complex scenes. For example, if you want to photograph a tiger in a cage, autofocus may focus on the cage instead of the tiger.

Advantages of digital camera lens

Because of the working mode of digital camera, the lens does not always need to be placed in the center of the standard front. In this way, some digital cameras provide a rotatable or detachable lens, such as Nikon COOLPIX995, which provides a triple optical zoom lens that can rotate 270 degrees, while Minolta Dimage V digital camera provides a lens that can be separated from the fuselage. This will make you more flexible when taking pictures.

control characteristic

Whether you are a camera fan or not, the control characteristics of the camera are very important.

Aperture and shutter

Most digital cameras are automatically exposed according to the program. Some high-end models also provide automatic exposure with aperture priority, that is, you first choose the aperture setting, and then the camera adjusts the shutter speed according to the light when taking pictures, thus providing correct exposure. Most cameras have at least two aperture settings-usually one for dim light and one for bright light.

If you are an experienced traditional camera photographer, you may want to compare the aperture settings and shutter speeds provided by various cameras. If you are really a master photographer (or will become a master one day), you will want a camera with manual exposure adjustment option. Usually, this adjustment is provided in the form of exposure compensation, so that you can choose to increase or decrease the exposure settings based on the automatic exposure mechanism.

Photometric mode

Another exposure-related factor to be considered is the metering mode of a digital camera, which determines how to estimate the available light when the camera determines the correct exposure.

Some high-end digital cameras allow users to select different exposure metering function files. Please read your camera manual to find out which buttons or menu commands can be used to select different function files. ) Simply put, the so-called photometric function refers to a method of photometric calculation of scene light by using the camera's automatic exposure mechanism, that is, to calculate the correct exposure data when taking pictures. Several common measurement methods are:

Matrix or multi-area measurement. Sometimes this method is called multi-area photometry. The framing area is divided into small cells (matrix), and the light of many different points in each cell is analyzed. Based on this, the camera selects the comprehensive optimal exposure data of the bright and dark parts of the shooting scene. This function belongs to the standard default automatic exposure function file, which can take better images in most cases.

Center weighted photometer. It measures the light of the whole scenic spot, but pays more attention to the light of the central part of the scenic spot. This metering method should be used when shooting objects relative to the edge of the scenic spot and paying more attention to the central part of the scenic spot.

Spot metering It only measures the light in the central area of the scene. This method is most effective when the brightness of the background is higher than the brightness of the object, such as the background of the object you are shooting is very bright (the object is in front of sunlight or other light sources). If matrix photometry or center-weighted photometry is used, the subject may be overexposed, because the camera will reduce the exposure coefficient due to the brightness of the background.

Low-end digital cameras generally only provide one metering method, while advanced digital cameras allow users to choose three metering methods according to the shooting environment.

White balance regulation

Different light sources have different color temperatures. Color temperature is an esoteric statement, that is, a light source contains different proportions of red, green and blue light.

Color temperature is measured in degrees Kelvin. Unless you really want to discuss it with an experienced cinematographer or cameraman, you really don't need to understand its concept. The color temperature of sunlight at noon is about 5500 Kelvin, which is generally abbreviated as 5500K, not to be confused with 5500KB'. These two words represent two categories: technology, photography and computer respectively, and it is easy to cause confusion when they appear at the same time.

In any case, the color temperature of the light source will affect the color recognition of the subject by cameras (including video recorders, digital cameras and traditional film cameras). If you take pictures under fluorescent lights, you will find that the photos are a little green. This color comes from the color of fluorescent lamps.

Photographers of traditional film cameras can use special films or color filters to compensate for different light sources. But digital cameras, including video cameras, use a method called white balance to deal with the color temperature problem. White balance just tells the camera how the mixture of red, green and blue light can synthesize pure white light under the current lighting conditions. Based on these data, the camera accurately reproduces various other colors in the scene.

Most digital cameras can automatically handle white balance, but in some special situations (such as dusk and fluorescent lights), the effect is often not good. Therefore, most of the newer models of mid-to high-end cameras provide manual white balance adjustment.

Continuous shooting mode

Some low-end digital cameras need a few seconds to set autofocus and automatic exposure before shooting; In addition, it takes several seconds to process the image and save it in the storage device after shooting. If you need to use the flash, please wait a few seconds for the flash to charge. This undoubtedly brings inconvenience to taking pictures, especially when you want to capture some wonderful moments.

Therefore, some digital cameras can provide quick shooting function. Different brands or models of cameras are slightly different in this function. One of them is called 16 continuous shooting, that is, the camera can record 16 pictures on the same photo continuously by pressing the shutter once. Its disadvantage is that the resolution is not high and the flash cannot be used. Another continuous shooting mode allows you to press the shutter once and take a series of images instead of a few small pictures in a photo. At this time, as long as you don't let go of the shutter button, the camera will keep shooting at regular intervals. If your camera has this quick shooting function, you can check whether it can be set to take more or less images in a certain period of time. More advanced digital cameras have a cache device inside the camera, which allows you to shoot continuously at high speed in high resolution mode like high-end traditional cameras. Now most of the top models of some well-known digital cameras have this function.

Flash and control

Digital cameras generally have built-in flash, which can take pictures in dark or poor light. You can also set its flash mode according to your own needs, such as automatic flash, forced flash, red-eye flash and no flash. But at present, the flash index of digital cameras is mostly low, and the flash range is small (generally around three meters). Therefore, some high-end digital cameras are equipped with an external flash interface, which can be connected to the flash through a synchronous line or hot boots, while others are equipped with a slow synchronous flash setting, and digital cameras with adjustable flash index have begun to appear.

liquid crystal display

Most digital cameras have LCD screens. The LCD screen is like a microcomputer monitor, which can display the images stored in the camera. LCD is also used to display menus so that users can modify camera settings and delete unwanted images from camera memory. The function of viewing and deleting images on the camera is very useful because it saves time in downloading unnecessary images. If the photo you took is not what you want, you can delete it and take it again.

The LCD on most cameras can also be used to preview the photos you want to take (digital cameras of SLR cameras can't view through LCD due to optical structure, such as Olympus -2500L). So if your camera has a traditional viewfinder and LCD, you can use the LCD or viewfinder to select the border of the photo. When shooting close range, most cameras will force you to use LCD to avoid visual errors. A few cameras with LCD have no traditional viewfinder, so all photos must be composed with LCD. In fact, it is sometimes difficult to take pictures with LCD when shooting, because in order to see the scene, you have to hold the camera and keep it a few inches away from you. If your hands are not so steady, it is difficult to keep the camera still when taking pictures. It is especially important to use a tripod in this case.

Liquid crystal displays also have some disadvantages. It increases the weight of the camera, and they also consume the energy of many camera batteries. In addition, when you take pictures in bright light or from different angles on the front of the LCD, the LCD screen will become dim, making it difficult for you to see the pictures you want to take. However, this problem is gradually being solved. At present, some digital cameras use low-temperature polysilicon as LCD material, which greatly reduces power consumption and saves electricity. Some digital cameras also use wide-angle liquid crystal, which can be viewed clearly and brightly from different angles.

In addition, the pixel level of LCD is also an important factor to determine its quality. At present, the pixels of LCD of most digital cameras are above 1 10000, and these LCDs can generally reflect the details of images well. In order to reduce the cost, some digital cameras use low-pixel liquid crystal displays (the liquid crystal display of Fuji 2800 has only 60,000 pixels). The images displayed on these liquid crystal displays have obvious graininess, slow refresh speed and obvious lag in framing.

You can also visit some related websites, such as:/special/d/001618dk/dpindex.html.

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