Brief introduction of digital photography technology

The first chapter is an overview of digital cameras.

Digital camera, also called digital camera, is an integrated product of light, machinery and electricity. It first appeared in America. More than 20 years ago, the United States used it to transmit photos to the ground via satellite. Later, digital photography was converted to civilian use, and its application scope continued to expand. The core component of a digital camera is a charge coupled device (CCD) image sensor, which is made of highly sensitive semiconductor materials. It can convert light into charge, and the charge is converted into a digital signal through an analog-to-digital conversion chip. After the digital signal is compressed, it is saved by the flash memory or built-in hard disk card in the camera, so the data can be easily transmitted to the computer, and with the help of computer processing means, the image can be modified as needed and imagined.

The biggest advantage of digital camera lies in its digitalization of information. Because digital information can be instantly transmitted to the whole world through digital communication network, digital cameras can first realize real-time transmission of images.

As a computer input device, digital camera has made great progress in recent years. First of all, due to the progress of technology and technology, the resolution of digital cameras, which are the mainstream models of computer input devices, is generally in the order of millions of pixels. It looks almost the same as a traditional camera. Secondly, due to the increase of production and sales and the progress of technology, the price of digital cameras is also dropping rapidly. All these have promoted the popularization of digital camera applications, and then prompted manufacturers to invest more in technology and technology. This benign interaction makes digital cameras an indispensable device in computer applications.

The appearance, some functions and operations of digital cameras are similar to those of ordinary cameras. But there are several differences between digital cameras and traditional cameras:

The production process is different: as a photographic tool, the appearance of a digital camera is basically similar to that of a traditional camera, except that the traditional camera uses silver salt photosensitive material, that is, film, as the carrier, and the photographed film has to be developed to get photos. Just after shooting, the operator can't know the quality of the photos, so delete the bad photos. Under normal circumstances, the effect of photos processed in darkroom cannot be changed. A digital camera uses a charge coupled device (CCD) to sense light instead of film, and then converts the light signal into an electrical signal, which is recorded on a memory card after analog-to-digital conversion. The memory card can be reused. Because the photos taken by the digital camera need to be digitized before being stored, the photos taken can be played back and viewed, and the dissatisfied photos can be deleted immediately and re-taken. Connecting a digital camera to a computer after shooting can easily transfer photos to the computer for various processing, and then print them out through a printer, which is the main difference between a digital camera and a traditional camera.

The shooting effect is different: the silver halide film of traditional camera can capture continuous tones and colors, while the CCD element of digital camera will lose some details in dark or bright light. More importantly, the pixels of images captured by CCD elements of digital cameras are much smaller than those captured by traditional cameras. Generally speaking, the resolution of traditional 35mm film is 2,500 lines per inch, which is equivalent to 6,543.8+0.8 million pixels or even higher, while the best CCD used in digital cameras at present can not achieve 6,543.8+0.8 million pixels. At present, the photos taken by digital cameras are not comparable to traditional cameras in terms of clarity, texture, level and color saturation.

Shooting speed is different: you need to wait 1.5 seconds before pressing the shutter, that is, before the digital camera actually records data. This is because digital cameras need to adjust the aperture, change the shutter speed, check the autofocus and turn on the flash. Every time a digital camera takes a photo, it has to wait 3-7 seconds to take the next photo. This is because digital cameras have to compress the photos they take and store them. Due to the slow storage speed of the memory card, the shooting speed of the digital camera, especially the continuous shooting speed, can't meet the requirements of professional photography. Moreover, because every action of the camera needs power consumption, the power consumption of digital cameras is large. These are the shortcomings of digital cameras.

The storage media are different: the images of digital cameras are digitally stored on magnetic media, while the images of traditional cameras are chemically recorded on silver halide films.

There are different input and output methods: the images of digital cameras can be directly input into the computer for processing and printing. The image of a traditional camera must be developed in a darkroom, and it must be scanned into a computer by a scanner for processing, and the quality of the scanned image will inevitably be affected by the accuracy of the scanner. In this way, even if the original quality is higher, the scanned image is far from good. Digital cameras can easily capture all the moments in nature as digital images, which can be directly processed by computers and displayed on TV. Therefore, many computer or household appliance manufacturers, such as Hewlett-Packard, Sony, Apple and Sharp, are competing to produce digital cameras, and digital cameras are no longer just exclusive products of photographic equipment factories such as Kodak or Fuji. At present, several Japanese photographic equipment companies are trying to eliminate silver bromide films within five years. It is predicted that in the next 10 year, most people in the world will use digital cameras. Many multinational companies compete for the digital camera market precisely because they see the outstanding advantages of digital cameras, that is, it can benefit users in terms of speed, convenience, reducing the cost of pictures and improving efficiency.

China's digital camera market has only risen quietly in recent years. From the perspective of distribution brands, brand-name products are the main products, among which the most mainstream brands are fujifilm, Kodak, Olympus, Sony and so on. 1998 The total sales volume of digital cameras in China was about 40,000 sets, and 1999 is expected to exceed 60,000 sets. At present, the mainstream models of commercial digital cameras on the market are: Fuji MX-500/MX-600/MX-2900, Olympus 1400XL/2000Zoom, Kodak DC 240/DC 265/DC 240.

Digital camera users are mainly distributed in computers, communications, electronics, finance, transportation, culture, commerce, tourism, architecture, military police and government departments. For individual users, digital cameras are mainly used in tourism, photography and other aspects, and professional photography and convenient work users account for nearly half; As a unit user, it is mainly used for shooting work, followed by product introduction and advertising design, news interview, desktop typesetting and architectural decoration design.

With the increasing global digital craze, coupled with the gradual maturity of digital camera technology and the gradual decline in prices, digital cameras will become one of the fastest-growing industries in the IT industry.

The second chapter is the main performance indicators that affect the shooting quality of digital cameras.

Digital camera is a product integrating optics, machinery and electronics. It integrates image information conversion, storage and transmission, and has the characteristics of digital access, interactive processing with computer and real-time shooting. Many performance indicators of digital cameras depend on the concept of traditional cameras. However, due to the structural differences between digital cameras and traditional cameras, general manufacturers use the concept of "equivalent to traditional cameras" to describe them. This chapter will introduce in detail the performance indicators that affect the shooting quality of digital cameras (this part is similar to traditional cameras in many concepts).

Resolution of digital camera

Color depth of digital camera

Optical lens of digital camera

Lens focal length of digital camera

Aperture and shutter of digital camera

White balance of digital camera

Sensitivity of digital camera

Exposure compensation of digital camera

Exposure mode of BR> digital camera

1 resolution of digital camera

Compared with traditional cameras, traditional cameras use "film" as the carrier for recording information, and the "film" of digital cameras is its imaging device, which is integrated with the camera and is the heart of digital cameras. Digital cameras use photosensitive elements as imaging devices to convert optical information in images into digital signals. At present, there are two kinds of photosensitive elements: one is CCD (Charge Coupled Device), which is widely used; The other is a new CMOS (complementary metal oxide semiconductor) device. The resolution of a digital camera refers to the number of photosensitive elements in the camera. At the same resolution, CMOS is cheaper than CCD, but the image quality produced by CMOS photosensitive devices is lower.

At present, the common imaging devices of digital cameras on the market are CCD (Charge Coupled Device) and CCD image sensor. It is made of high-sensitivity semiconductor material, which can convert light into charge and convert it into digital signal through analog-to-digital conversion chip. The more transistors the CCD of a digital camera contains, the higher the resolution. The resolution of CCD—

The number of pixels is often used as the main basis for digital camera grading. It is true that the resolution of CCD determines the imaging quality of digital camera in a sense, but just as the granularity can't completely summarize the quality of film, the resolution is not the only criterion to evaluate the quality of CCD. The influence of its color depth and the manufacturing level of the chip itself on the final imaging quality should not be underestimated.

However, compared with other indicators of digital cameras, resolution is still the most important performance indicator of digital cameras. The resolution of a digital camera is measured by the absolute number of pixels of an image (not the number of pixels per inch DPI), because most digital photos use area CCD. The number of pixels of the image taken by a digital camera depends on the number of photosensitive elements on the CCD chip in the camera. The more numbers, the higher the resolution of the image and the higher the quality of the captured image. Of course, the price of the camera will increase in direct proportion. The resolution of a digital camera also directly reflects the size of photos that can be printed. The higher the resolution, the larger the printable photo size under the same output quality. For similar digital cameras, the higher the resolution, the higher the grade, but the more memory space it takes up. In addition, there are high requirements for the speed of processing and processing computers, the capacity of memory and hard disk, and the corresponding software.

From the perspective of CCD chip manufacturing technology, the smaller the chip area, the higher the integration level, the better, although some people think that the larger the chip area, the better the imaging quality when the optical resolution of the lens is limited and the number of CCD pixels is fixed. However, judging from the actual shooting effect of digital cameras at present, the relative image preference of digital cameras that generally use small-chip CCD may be because the high-integration CCD is superior in original materials and technology.

When understanding the resolution of digital cameras, we must distinguish two concepts of resolution, one is the resolution of CCD (or pixel value), and the other is the resolution of captured images (the maximum resolution of images indicated by general manufacturers). These two resolutions, in principle, the resolution of CCD determines the maximum resolution of the image, but these two resolutions are generally not equal.

If you choose a digital camera, you must pay attention to that the resolution (pixel) of CCD is the most important index. When the maximum resolution of the captured images is the same, the larger the resolution of CCD, the better. For example, for a camera with the same image resolution as (1280* 1024), the shooting quality of a CCD camera with10.5 million pixels will be better than that of a digital camera with1410.0 million pixels. This is because, as a photosensitive device, when the pixels at the edge of CCD are shooting, due to the influence of edge light, color cast and dizziness generally occur. When the CCD pixel is larger than the image shooting pixel, the digital camera will automatically cut off the edge pixels to remove dizziness and color cast, and the more trimming, the better.

This is why manufacturers use 14 10000 pixels or even 150000 pixels for maximum shooting1280 *1024 (1310000 pixels. Therefore, manufacturers who pursue quality generally use CCD, and the accuracy is much higher than the maximum accuracy of shooting images.

At present, there are many cameras, and the accuracy of shooting images (such as 1200* 1800) is much higher than that of CCD (13 10000 pixels). This is done by software interpolation (the function of any image software), so the image accuracy is not ideal at all. Increasing the accuracy of the software can only blur the details of the image. If it is a big picture printing, the definition is often not satisfactory, especially the details are very poor. So when you buy a digital camera, you can only measure the quality of the camera by the accuracy of CCD. Otherwise, you may buy a 13 1 10,000 pixel digital camera as a 2 million pixel camera.

Photo resolution manufacturers will indicate the maximum resolution of their cameras, such as 1280× 1024. Users can also reduce the resolution and save more photos on the same memory card. Photos for different purposes can use different resolutions and compression ratios. The more choices, the better. Here I want to make it clear that the same resolution can have different compression ratios, and both resolution and compression ratio determine the quality of photos, which readers should pay attention to. Of course, quality and quantity are a pair of contradictions on the same memory card, and users need to choose appropriately.

2. Digital camera color numbers

The number of color bits is also called color depth. The color depth index of a digital camera reflects how many tones a digital camera can record correctly. The higher the number of color bits, the more likely it is to restore the details of the bright and dark parts. At present, almost all digital cameras have 24-color numbers, which can generate true-color images. Some are called 30-bit or 36-bit, but the actual CCD is also 24-bit. At present, the CCD of commercial digital cameras is 24-bit. Therefore, this index is not the key index to measure digital cameras at present, and it does not need to be considered in general applications.

3. Optical lens of digital camera

For cameras, the quality of the lens has always been a key factor affecting the imaging quality, and digital cameras are no exception. Although the CCD resolution of digital camera is limited, the optical resolution of lens is low in principle; On the other hand, because the imaging area of digital camera is small (because digital camera images on CCD, which is much smaller than the film of traditional 35mm camera), lens is needed to ensure a certain imaging quality. For example, a subject needs 200 pixels in the horizontal direction to perfectly reproduce its details. If the imaging width is 10mm, a lens with an optical resolution of 20 lines /mm is enough. If the imaging width is 1mm, the optical resolution of the lens must be above 2000 lines /mm. On the other hand, traditional film is sensitive to ultraviolet rays, so it is often necessary to install a UV mirror when shooting outdoors, while CCD is sensitive to infrared rays. Adding a special coating or filter to the lens will greatly improve the imaging quality. The physical aperture of the lens must also be considered, and regardless of its relative aperture, the larger its physical aperture, the greater the luminous flux, the better the digital camera accepts and controls the light, and the better the imaging quality.

At present, some manufacturers have adopted relatively good lenses for commercial or household digital cameras. Fuji camera adopts professional Fuji Dragon lens with resolution of 170 lines/mm. This new built-in Fuji Dragon lens is clearer than most SLR lenses. Not only does it ensure the quality of image shooting in accuracy, but its lens error rate also reaches an astonishing 0.3%, which is 2/3 lower than that of ordinary digital cameras.

In addition, in some digital cameras, there are also two lens modes: telephoto and wide angle. This is also a reference index when you choose a digital camera.

In traditional digital cameras, wide-angle lens is a photographic lens with shorter focal length, larger viewing angle, longer distance and smaller viewing angle than standard lens. Wide-angle lenses are divided into ordinary wide-angle lenses and ultra-wide-angle lenses. 135 camera's common wide-angle lens has a focal length of 38-24 mm and a viewing angle of 60-84 degrees. The ultra wide-angle lens has a focal length of 20- 13mm and a viewing angle of 94- 1 18 degrees. Because the wide-angle lens has a short focal length and a large viewing angle, it can shoot a large area of scenery in a short shooting distance. Therefore, it is widely used to shoot large-scale landscape photography. In photography creation, using wide-angle lens to shoot can achieve the following effects: first, it can increase the sense of spatial depth of photographic images; Second, the depth of field is long, which can ensure that the scene before and after the subject can be clearly reproduced on the screen. Therefore, the vast majority of modern pocket automatic cameras (commonly known as fool cameras) use ordinary wide-angle lenses of 38-35 mm; Third, the lens covers a large area and shoots a wide range of scenery; Fourthly, the scene shot at the same shooting distance is smaller than the scene image shot with the standard lens; Fifth, perspective distortion and image distortion are easy to appear in the picture. The shorter the focal length of the lens and the closer the shooting distance, the more obvious this defect is.

At present, most commercial digital cameras use the same general wide-angle lens as ordinary 35 mm cameras. A digital camera with the same performance will perform better when choosing a digital camera because of its advantages such as deep scene and wide shooting range. At present, digital cameras with wide-angle shooting function include Fuji MX-600, Kodak DC265, Olympus 1400XL and so on.

4. Lens focal length of digital camera

Digital cameras, like human eyes, capture everything in the world through the lens. If the human eye has an error (myopia) in the focal length, it can't distinguish things correctly. As the lens of a digital camera, its most important characteristic is also the focal length of the lens. The focal length of the lens is different, the breadth of the scene that can be shot is different, and the photo effect is also very different. If you often use an ordinary 35 mm camera, you should have a basic understanding of the lens focal length of the camera. For example, you usually take scenery and commemorative photos with a lens of about 35 mm, and take photos with a lens of about 80 mm to identify the "big head" you need. Compared with traditional cameras, because digital cameras use CCD photosensitive devices, the focal lengths indicated on their lenses are usually 5.0 mm, 10 mm, etc. In ordinary 35 mm cameras, super wide-angle or fisheye lens is generally used, while the lens commonly used by digital camera manufacturers is only a small wide-angle lens equivalent to 35 mm cameras.

To explain this problem, we must first talk about the relationship between lens angle and focal length. The included angle between the central node of the lens and the diagonal ends of the imaging plane is the diagonal viewing angle of the lens (see attached figure).

It is not difficult to see that for the same imaging area, the shorter the focal length of the lens, the larger the viewing angle; For a lens with the same focal length, the smaller the imaging area, the smaller the viewing angle of the lens. The imaging area of 35mm camera is equal to the photosensitive area of 135 film-the standard 36× 24mm. Digital cameras use CCD sensor to replace the position of film in traditional cameras, but its area has several specifications, ranging from 18.4× 27.6mm for high-grade professional cameras to 2/3, 1/2 and 6556 for ordinary digital cameras. In other words, the same lens has a wide-angle effect on some digital cameras, but it may become a standard lens on other cameras. It seems inconvenient for us to distinguish the visual angle of digital camera lens by focal length value, so digital camera manufacturers usually provide a relatively easy-to-compare value, that is, mark the focal length of 35 mm camera lens with the same visual angle as digital camera lens, so that we can easily understand the corresponding focal length value. A lens like Fuji MX-500 has a focal length of 7.6 mm and a diagonal viewing angle of 70 degrees, which is equivalent to a 35 mm lens and is a small wide angle. Fuji's MX-600 is equipped with a small wide-angle zoom lens equivalent to 35- 105 mm. When evaluating and purchasing digital cameras, we only need to refer to the lens focal length converted into 35mm cameras. What is the actual focal length of the lens is basically irrelevant to us, and you can't calculate it in detail. In fact, the optical zoom factor of digital camera can basically reflect this index. Although there will be some differences between different types of digital cameras, the differences will not be too great. If you don't deliberately pursue a specific focal length equivalent to a 35mm camera, refer to the optical zoom multiple of a digital camera.

Maybe some users still don't know the actual focal length of the digital camera lens, because if it is 7.6 mm focal length on a 35 mm camera, it is an extremely rare fisheye lens, it must be huge and expensive, and the photos taken are seriously distorted and have a strong sense of perspective. But the 7.6 mm lens on the digital camera is the size of a thumb, and the whole digital camera is much cheaper than the traditional lens. Although only a small piece in the middle is used for imaging, the exaggerated fisheye effect makes people feel drums about its image quality. In fact, this kind of worry is unnecessary. The lens diameter of 35mm camera is very large to ensure the imaging quality around the picture, while the area of CCD is much smaller than that of film. To achieve high-quality imaging in a small area, only a small lens size is enough. Moreover, what actually determines the lens structure is its effective viewing angle, not the simple focal length value. The 7.6 mm lens on digital camera adopts the design of 35 mm small wide-angle lens on traditional camera, instead of the structure of 7.6 mm fisheye lens. Therefore, the focal length of digital camera lens is not directly related to the actual imaging effect. Because the volume of the lens is small, the relative cost is also reduced, but higher imaging quality can be easily realized.

5. Aperture and shutter

Like traditional cameras, the aperture range and shutter speed of digital cameras are very important when shooting, but for ordinary commercial and domestic digital cameras at present, people only care about how to choose the shooting scene because of the full automation of the cameras, but don't pay much attention to the aperture and shutter speed automatically controlled by the cameras. However, if you buy a digital camera, you'd better compare the aperture range and shutter speed of various digital cameras, because the aperture and shutter will cooperate to control the overall light entry range of your digital camera, which means that it will affect whether your camera can get good results in various light conditions. At the same time, the shutter speed will directly affect the effect when you shoot dynamic images, and the aperture range will affect the depth of field of your shot images.

The process of taking pictures is that after the camera opens the shutter, the front image is projected onto the CCD photoreceptor of the digital camera through the lens, and the photoreceptor records the image information on the memory card of the camera through the digital-to-analog converter. This process is the same as the traditional camera exposure process. However, in order to get rich images, it is necessary to control the amount of light projected on the CCD sensor so that the details in the photos can be described correctly. From the darkest to the brightest area, there are rich levels of expression, and there is a gradual transition between light and dark, which is not completely black and white. In addition, the contrast and freshness of the works also have the best table? . Too much light leads to exposure transition and the image is obviously bright; On the other hand, if the CCD absorbs too little light, it will be underexposed, the whole photo will be dark, the details will be lost, and the photo effect will be quite bad, so it is very important to get the appropriate exposure when shooting.

Like traditional cameras, digital cameras are used to control exposure, that is, "aperture" and "shutter". Aperture is the aperture through which light passes through the lens. The larger the aperture, the more light can be projected per unit time, and the shutter is the time for light to pass through the lens. The shorter the time, the smaller the exposure.

Like traditional cameras, digital cameras have an aperture placed in several lenses of the lens, which is composed of several metal sheets, and the aperture is adjusted by the movement of the metal sheets. Anyone who has used traditional reflective cameras knows that on the lens, we can find the aperture value f, which is usually? The aperture ratio of is:1.4,2,2.8,4,5.6,8, 1 1,16,22 ... The larger the aperture series f, the smaller the aperture of the lens, and the value of f is the distance between the lens focal length and the aperture (the size of the aperture) Word, so the larger the value, the smaller the caliber. But at present, in some digital cameras, the aperture is not set according to the above series, but according to f2.8, f.5.6, f 1 1. At this time, the light input of the upper and lower layers is not only twice as bad.

As mentioned earlier, the aperture is the size of the aperture when light passes through the lens. However, this is only a general statement. The aperture size should also consider the focal length of the lens itself. The lens length of a long focal length lens (telescope head) is long, and the distance from the entrance of light to CCD is long, so the light projected on CCD is weak, so the aperture of a long focal length lens is often slightly smaller. If you want to make a lens with a larger aperture, you must? Only by increasing the aperture can the unit light input be increased. However, due to the difficulty and high manufacturing technology of large aperture lens series, this kind of lens is usually expensive. Because the aperture series f is calculated by the ratio of aperture size to focal length, as long as the aperture series is the same, the amount of light entering is the same whether it is 35 mm or 200 mm

Shutter speed values are usually marked as: 1, 2, 4, 8, 15, 30, 60, 125, 250, 500 ... These are the reciprocal of 1 second, so 15 means 650. The light value of 1/500 seconds is half that of 1/250 seconds, and only 1/4 of125 seconds.

Because both aperture and shutter can be used to control the exposure, as long as the aperture value f is determined, the exposure can be corrected by the shutter speed. On the contrary, you can go first? After setting the shutter speed, we can get exposure by adjusting the aperture. Fortunately, the adjustment of light quantity is controlled by the concept of twice, which makes it easier for us? Adjust the appropriate exposure, such as? : If the measured correct exposure is f/ 1 1, how fast? At 1/30s, if you want to raise the shutter to 1/60s, the aperture will be enlarged to f/8, because when the shutter is from 1/30s to 1/60s, the exposure time will be reduced by half, so the aperture will be enlarged by one level, which will increase the light input per unit time.

However, because the aperture and shutter have their own advantages, the effect produced by each collocation is different. We must choose the most suitable combination according to the needs of the subject and the way we want to express ourselves, so as to give full play to the practical significance of aperture and shutter.

According to shutter speed, it can be divided into high-speed shutter and slow shutter. Usually, a high-speed shutter can "fix" a moving object, and the action details and textures of the fixed object are vividly portrayed, making the object more stereoscopic. Usually the shutter speed is from 1/30 seconds to 1 second, or even faster than 1 second. Are they all fast and slow? The first method is to fix the camera, and then use the slow shutter speed to make the moving objects produce blurred images, so that the clarity of the background (still life) can better set off the dynamics of the theme. The second method is to make the camera translate or shift with the direction of the object movement. In this way, contrary to the first method, the background will become quite vague, while the theme will be a little vague but clear, which will also separate the subject from the background. The third kind, that is, the whole photo is blurred without stopping, and the phase machine is shaken quickly. These three methods have their own characteristics, and how to use them in time depends on everyone's preference.

We often shoot the city at night with a slow shutter, because the driving vehicles leave traces of red and white lights, and dozens of lights gather into a long queue, which is very beautiful and depicts the prosperity of the city that never sleeps. It is still used to shoot running water, and it feels quite soft and delicate.

Pay special attention when choosing the slow shutter, because the exposure time of each stage of the slow shutter is very different, unlike 1/250 seconds and 1/500 seconds of the high-speed shutter. The effect is difficult to compare. When shooting a flowing scene with a slow shutter, if the shutter is too fast, the scene will freeze unexpectedly. If the shutter is too slow, it will look too hazy and lose the watch you want. Effect, so try the slow speed of each grid? If you film them all, you can get the ideal works and see the differences.

Compared with the shutter, the aperture is a little more complicated. In addition to adjusting the exposure, the most important thing is to control the size of the "depth of field" of the picture. The so-called "depth of field" means focusing to make the image clear. There is an area within a certain distance before and after, which can be clearly displayed. This range is called depth of field. The longer the depth of field, the larger the range that can be clearly displayed. On the contrary, the smaller the depth of field, the more blurred the foreground or background, which is a hazy phenomenon caused by poor focus. From the optical theory, under the focal length of the lens, only the plane at the object distance can be clearly shown, and the scenery outside this plane will be blurred.

The depth of field of an image has three factors: (1) The depth of field is inversely proportional to the length of the focal length, in other words, the longer the focal length of the lens, the shorter the depth of field. (2) The depth of field is proportional to the shooting distance of the scene. The closer the camera is to the scene, the shorter the depth of field. (3) The depth of field is proportional to the aperture series. If the focal length of the lens and the shooting distance of the object are inconvenient to maintain, then the larger the aperture, the shorter the depth of field, that is? The aperture is from f/16 → f/1→ f/8 → f/5.6 → f/4 ... The depth of field is getting shorter and shorter, and the scenery outside the depth of field is more blurred, but the subject in correct focus is vivid and eye-catching. The messy scenery before and after beautifies the hazy beauty, which is different from the blur caused by camera vibration. Full of elegant and soft luster, just like the rendered colored ink, it makes the tone lighter and can create a considerable atmosphere and depth of field. The theme of separation? Feeling, with the characteristics of setting off the subject, is often used in portrait photography, and the background of the model is blurred, which makes people focus on the beautiful model. At the same time, because of the large aperture, there can be more light, thus improving the shutter speed, preventing camera shake and making the image sharper and clearer. And if you are in a dim light source, you want to capture the environment and atmosphere at that time without the help of a tripod, or you can't use a slow shutter.

If the aperture is smaller, from f/5.6 → f/8 → f/1→ f/16 → f/22 ..., the range of depth of field will be larger, the description of the scene will be more realistic and full of authenticity, and the picture quality will be clearer and Ming Rui than that of a large aperture, and because of the range of depth of field, Reduce aberration to obtain high-quality works. Small aperture can reduce shutter speed and change from slow to fast. Create a sense of mobility.

For professional digital cameras, it is generally possible to manually control the aperture and shutter speed of the camera, but for commercial and household digital cameras, because the camera automatically controls the aperture and shutter speed, it is not necessary to control it by itself.