Seeking knowledge about digital cameras

Canon's power shot A series cameras have always been known for their high cost performance. At present, A6 10 has the best cost performance. You can learn about it.

Your shutter speed of "2-11000 seconds" is generally enough, so don't worry too much.

The main parameters to look at when choosing a machine are lens and CCD, which are the key components of a digital camera and cannot be ignored.

Digital camera selection guide-lens selection ★ lens

Among the physical components of digital cameras, the lens is a very important one, and its quality is the key factor affecting the image quality. In the purchase of digital cameras, lens material, focal length and zoom ability are three main parameters. At present, the lens materials of digital cameras are mainly glass and plastic. Although the image projected by all-glass lens is the clearest, it doesn't mean that the camera with glass lens is necessarily better than the plastic one. This is because optical imaging is quite complicated, which is influenced by the design of lens group to some extent. Moreover, glass material is heavier than plastic material, which may also affect the overall weight of the camera. So when you buy a glass lens, don't think that it has absolute high quality, but also make a comprehensive observation from many aspects.

In the technical specifications of digital cameras, the parameter of focal length is generally marked as F value (representing the maximum aperture) and F value (representing the focal length). The focal length usually includes the design value of the camera itself, which is equivalent to the focal length value of an ordinary 35mm camera, such as f=8 to 24, which is equivalent to 38- 1 15mm of the 35mm camera. Generally speaking, a 35mm standard lens is 28-70mm. If it exceeds 70mm, it means that the lens has telescopic function; if it is less than 28mm, it has wide-angle effect. At present, most mid-range digital cameras have optical zoom lenses, but the zoom range is very limited, rarely exceeding 10 times, so such cameras can generally be equipped with telephoto lenses and filters. Some digital cameras also have digital zoom function, which can expand the zoom range again, but you should pay attention that digital zoom only enlarges the pixels, and the actual optical resolution has not changed at all. For the zoom lens, the general household digital camera can zoom 2 ~ 3 times. In fact, for the zoom function of digital cameras, the zoom lens is not necessarily better than the fixed focus lens at a certain price. Because the design of zoom lens is complicated, it will be inconsistent in each focal length segment, while the design of fixed-focus lens is much simpler and performs very well in a fixed focal length segment. In addition, my personal opinion is that the product quality of traditional professional camera manufacturers is better.

Guide to digital camera purchase-CCD and LCD purchase

★ Photosensitive imaging element

Generally speaking, the imaging system of digital camera includes four parts: lens, aperture, shutter and photosensitive imaging device, among which photosensitive imaging device is the core component and the most expensive one, which can be called the heart of digital camera. At present, the photosensitive elements of digital cameras mainly use two kinds of photosensitive elements: CCD and CMOS. Compared with CMOS, under the same pixel, CCD consumes a lot of power and is expensive, but the image quality produced by CCD photosensitive devices is much better, so it has become the mainstream of the market. We mainly introduce a digital camera with CCD as imaging device.

There are two kinds of CCD: area CCD and scanning linear CCD. The CCD chip of area CCD digital camera has the advantage of fast shooting speed, which can shoot moving scenes and adapt to the environment with flash. The resolution of CCD chip used in scanning linear CCD digital camera is extremely high, but due to the scanning process, the higher the resolution, the longer the exposure time is required, which leads to the inability of this kind of digital camera to shoot moving scenes or flashlights. Therefore, unless it is only used for still life shooting, you should generally choose an area CCD digital camera. Regarding CCD, an important parameter used to distinguish the grade of digital camera is "pixel value", which depends on the number of photosensitive elements on the CCD chip. The more numbers, the higher the resolution of the image and the higher the quality of the photos taken. So when you buy a digital camera, you must remember that you can only use CCD pixels to measure the quality of a digital camera, but not other indicators. In addition, we can often see that CCD is expressed by fractions, such as 1/2 inch CCD, 1/2.7 inch CCD. From the actual shooting effect, the imaging quality of digital camera using small chip CCD is relatively good. This is because the smaller the chip area, the higher the integration, and the CCD with high integration is generally better in raw materials and technology.

★ LCD screen

At present, most digital cameras have color LCD screens, which are usually 1.8 inch or 2 inch for viewing, previewing and deleting photos. Some models can provide a visual experience as large as a 2.5 inch LCD screen. Although you can get many benefits of viewing, previewing and deleting images at any time through LCD, it also brings some inconvenience, because it is a very power-consuming device on digital cameras, and four ordinary batteries can only image about 15 (turn on LCD or use LCD to see the results after shooting), so the investigation of LCD is mainly about its energy saving. At present, some digital cameras use energy-saving lighting LCD screens to display images by collecting external light sources. Although the brightness of this LCD screen is poor, it reduces the energy consumption, greatly prolongs the service life of the battery and saves the cost, so you'd better choose this LCD digital camera when purchasing. In addition, whether the position of the LCD screen can be adjusted is also very important, because if the LCD screen of a digital camera can be folded or rotated, the LCD screen will give the photographer more freedom when taking pictures and the shooting effect will be better.

Digital camera selection guide-aperture and shutter selection

★ Aperture

Aperture is another extremely important physical component of digital camera. After all, a digital camera is still a camera. No matter how good the lens is, there will be no ideal effect without a good aperture, which is the same reason that advanced cameras can't take good photos with low-grade film. Aperture and shutter are closely related. The original quality of image shooting comes from the control of exposure, which is affected by both aperture and shutter. In the technical specifications of digital cameras, we should generally pay attention to its maximum aperture value. The larger the aperture design, the better the light transmittance, for example, 8-11000 sec, which means that its shutter can be opened for 8 seconds at the longest, which is suitable for night shooting, while the shorter the shutter opening time, it means that it can be shot instantly or quickly. A good digital camera will automatically calculate the aperture size according to the results of photometry. Generally, the faster the shutter speed, the larger the aperture, so that enough light can pass through, so it is also suitable for shooting high-speed moving objects, such as moving cars and falling water droplets. In addition to using a faster large aperture shutter, there is another advantage that it is easier to create a depth of field effect. As for what is the depth of field, simply put, if the subject is clear and the background is blurred, it is the depth of field of the scene, on the contrary, if the background is clear, it is the depth of field. The larger the aperture, the shallower the depth of field, which can highlight the main effect. In fact, most cheap digital cameras have a big disadvantage that the aperture is relatively small, and many of them are below F5, so it is difficult to take good photos in the case of insufficient light, so you must pay attention to choosing a digital camera with an aperture at least above F5 when purchasing.

★ shutter

When choosing a digital camera, the shutter is as important as the aperture. Shutter speed is an important parameter of digital camera shutter, and the shutter speed of different models of digital cameras is completely different. Therefore, when using a certain type of digital camera to shoot a scene, we must first know the shutter speed, because only by considering the start time of the shutter and grasping the release time of the shutter can we shoot a vivid picture. Usually, the shutter of ordinary digital cameras is mostly within11000 seconds, which can basically cope with most daily shooting. Shutter should not only look at "fast" but also "slow", that is, the delay of shutter. For example, in some digital cameras, the longest shutter is 16 second, which is enough for shooting at night. However, too long shutter will also increase the "noise" of digital photos, that is, there will be miscellaneous stripes in the photos. In addition, mainstream digital cameras must have aperture priority mode and shutter priority mode in addition to automatic shooting mode. Aperture priority mode is that the user decides the size of the aperture, and then the camera calculates the size of the light gate according to the ambient light and exposure settings. This mode is more suitable for shooting still objects. Shutter priority mode is that the user decides the shutter speed, and then the digital camera calculates the appropriate aperture size according to the environment. Therefore, shutter priority mode is more suitable for shooting moving objects, especially digital cameras are very sensitive to vibration, and even slightly shaking the camera during exposure will produce blurred photos, which is more obvious when using practical long focal length. When choosing a digital camera, it is best to choose a model with these modes to ensure the shooting effect.

Digital camera selection guide-flash card selection

★ Flash

Flash is a device used for lighting when shooting indoors or in low light environment, and its type varies with different digital cameras. Most digital cameras have built-in adjustable flash instead of external flash, but the illumination range of built-in flash is very limited compared with external flash equipment, and its average illumination is less than 10 foot, so the control method of flash is very important. Generally speaking, the control modes of digital camera flash are: off/on/auto, red-eye reduction, flash synchronization, hot boots and so on. Among them, Off/On/Auto is the most basic flash setting in digital cameras, that is, the flash is always off or on, and Auto is automatic flash; Red-eye reduction mode is used to reduce or prevent red eyes of people in pictures; Flash synchronization (flash and shutter synchronization devices) can be used to connect additional flash devices to provide sufficient lighting and synchronize with the shutter. Of course, many digital cameras have traditional flash devices besides flash synchronization, such as automatic flash. Finally, Hot Shoe is also used to add extra flash settings. Similarly, many digital cameras have both traditional flash and hot-shooting function modes. To sum up, the inspection point of the flash is that a digital camera with good functions should be able to support various flash control modes. If people often take pictures, you must choose a digital camera with the function of eliminating red eye to prevent the human eye from being photographed as a rabbit eye. This aspect is basically the same as ordinary cameras.

★ Storage medium

Storage media is another important part of digital cameras, which can be generally divided into built-in and mobile. The built-in storage medium is solidified with the digital camera. Its advantage is that once you have a digital camera, you can shoot without additional storage media. The disadvantage is that once the storage is full, you must enter the computer to release the storage space before shooting. Removable storage media are storage media that can be loaded or taken out at any time, and can be replaced at any time after storage is full. In addition, some digital cameras have both built-in and removable storage media, so they are relatively high-end. At present, most mainstream digital cameras on the market use removable storage media, mainly including floppy disks, PC(PCMCIA) cards and Compact? Flash cards and smart media cards. There is no doubt that the larger the storage medium, the better, because the larger the storage capacity, the more photos the digital camera can not output. Of course, it is not the best way to increase the storage capacity of photos simply by increasing the capacity of storage media (you should know that storage media is very expensive). More photos can be stored in storage media or camera memory, and appropriate compression formats can be adopted. However, the greater the compression ratio, the greater the image distortion, especially after the photo is enlarged, which is easy to produce color degradation, shadow and highlight separation, edge and detail effects are not obvious. Generally speaking, under the condition of the same storage medium capacity, JPEG format can store more images with lower image quality, while TIFF format can obtain higher image quality, but the storage capacity of photos is the least. At present, most digital cameras on the market are equipped with a storage medium with a capacity of 32MB, which is enough to take dozens of photos continuously, but if conditions permit, you'd better have a storage medium with a capacity of more than 256MB.

Guide to digital camera purchase-selection of battery output interface

★ Battery

Battery is also the key configuration of digital camera. At present, there are mainly alkaline batteries, rechargeable nickel-metal hydride batteries, rechargeable lithium batteries, external batteries and alternating current, among which rechargeable batteries include bulk nickel-metal hydride batteries, columnar lithium batteries and external batteries. Most digital cameras use four No.5 batteries, which can only image about 15 (turn on the LCD or use the LCD to see the results after shooting), and the low-end batteries are dead when they are less than 10, so the power consumption of digital cameras is very high. Please be sure to check the battery provided with the product when purchasing. This mainly examines the storage capacity of the battery, that is, the nature and support time of the battery. The types of batteries used in digital cameras can generally be divided into two types: the special type is usually lithium battery, which has good performance and long shooting time, which is beneficial to saving shooting cost, but charging and maintenance are more troublesome and the cost of purchasing spare batteries is higher; In contrast, general-purpose batteries are more suitable for home users and easier to buy than special-purpose lithium batteries, especially Ni-MH batteries, which can be recharged because they have no memory, and the price is cheap (four batteries of imported brands are probably around 500 yuan, and domestic ones such as "Motorized Altman" batteries with chargers are only 100 yuan), which are still relatively valuable. Generally speaking, due to the large power consumption of digital cameras, especially when taking pictures with LCD screen, it can be considered whether the camera is equipped with external power supply, charger or rechargeable battery. Whether the rechargeable battery is a special lithium-ion battery or a universal nickel-hydrogen battery depends on the use of your digital camera, but now most high-end digital cameras are using special batteries, which will become a trend. Finally, you should pay special attention to the energy saving of digital cameras. Energy-saving models can relatively extend the service life of batteries, thus further reducing battery costs.

★ Output interface

Images taken by digital cameras generally need to be sent to a computer for processing, so digital cameras have output interfaces but adopt different transmission methods. At present, the main transmission modes are 3.5-inch floppy disk, removable storage, infrared port (IrDA), serial port, parallel port and USB interface. Nowadays, digital cameras at home usually use RS-232 serial port for output, and almost all of them have video output interfaces, so you can enjoy the pictures taken on TV. The advantage of this port is good versatility, but the disadvantage is slow speed. Parallel port is also a common port in digital cameras. Its transmission speed is faster than serial port, but slower than USB port. In contrast, the transmission speed of USB port is much faster than that of serial port and parallel port, but it requires higher machine performance, but fortunately, few people use "prototype" below 586. In addition, infrared port (IrDA) is used in some digital cameras. This port uses infrared rays invisible to human eyes to complete the transmission task. It can transmit images without cables, provided that your computer also has infrared data association, and you have to put up with its extremely slow transmission speed. As for the latest standard high-speed serial port IEEE 1394, although the interface speed is extremely fast, it can also transmit video on it, but the number of digital cameras used is still relatively small, and it is surprisingly expensive, so I won't say much. In short, if you want to check the output port of a digital camera, you'd better choose a product with both USB port and parallel port or serial port. As the saying goes, be prepared.