What should photography know?

Know about digital cameras 1. There is no difference in optical principle between digital camera and traditional camera. They all form an object image on the focal plane through the lens. However, in the specific imaging, it is different because of different photosensitive media. Traditional cameras use photosensitive chemical media based on silver iodide distributed on film. Digital cameras use CCD as the photosensitive medium for recording images, and CCD records the visual characteristics of objects through different charge distributions caused by different illumination. Therefore, the images taken by digital cameras can be directly input into the computer without buying film, and the shooting effect can be seen at any time when shooting. If you are dissatisfied, you can retake them immediately. This has many advantages over traditional cameras, such as cost saving, digitalization convenience, and reduction of false shooting. The appearance of digital camera is mainly due to the invention of CCD charge coupler. CCD is actually a photosensitive plate, which is covered with photosensitive elements, that is, charge coupled devices. The digital camera uses the shutter to activate the CCD sensor, which converts the optical signal into an electrical signal and the illumination intensity into a corresponding value. Then the electrical signal is converted into a digital signal and processed, and finally the obtained digital image is stored in a memory. In fact, CCD itself can't distinguish colors, so color filters are needed in practical applications. Generally, different colors are coated on the filter layer of CCD devices. The different color blocks on the filter are arranged like a mosaic in the order of G-R-G-B (green-red-green-blue), so that the pixels under each mosaic can perceive different colors. When the light passes through the red, green and blue filters, the response value of each color light can be obtained. Then, by processing the obtained data with software, the color of each pixel can be determined. The image obtained by digital camera is actually a collection of values, so it can be downloaded directly to the computer for processing. The point here is that the light should be strong enough. Ordinary digital cameras, especially those that are cheaper, are powerless when the light is weak to a certain extent. Generally speaking, the stronger the light, the better. The digital image generated by CCD is transmitted to another internal chip of the camera. The chip is responsible for converting the image into the camera's internal storage format (generally compressed image format, such as JPEG format). Finally, the generated image is saved in memory. The first step in digital photography is to know what clarity means. Is this an absolute concept? Because we have different requirements, we have different concepts of clarity. There are three concepts here, namely focusing accuracy, depth of field selection and jitter. Focusing accuracy, there is nothing to say about the current dc AF, unless the subject you want to shoot is not in the focus range of the camera, or the scene is extremely dark, AF can still guarantee the quality. Unless you have higher requirements, such as getting hyperfocal distance. These are advanced technologies and should be discussed in Wuji instead of here. Second, the depth of field. Speaking of depth of field, we need to give another concept: diffusion circle, noun explanation: diffusion circle: diffusion circle. Before and after focusing, the light can't converge to one point, and the image of the point becomes a fuzzy enlarged circular spot. The outer circle of this spot is called the diffusion circle. Obviously, when the size of the dispersion circle is small enough, the human eye will think it is an indistinguishable point. At this time, we will feel a distance before and after the focal segment, and all the images are very clear. This produces a "depth of field". The concept of dispersion circle in depth of field is called allowable dispersion circle, which changes with the change of human observation resolution, and the depth of field changes with the acceptability of dispersion circle. For a steady camera, I can do it now: at the focal length of 50mm relative to 135, when I hold steady 1/4 seconds, I may not see jitter on the LCD, and when I hold steady1125 seconds, I can't see jitter when I zoom in to 7 inches, and zoom in to A3. The correct hand-held method is to level the viewfinder with the eyes of the camera. At this point, your left hand holds the camera's left elbow tightly and supports it at the rib to form a 3-angle, while your right hand holds the handle tightly and supports your right elbow tightly at the rib, which is also a 3-angle. At the same time, the two arms naturally form 3 angles. People with some knowledge of physics should have felt its stability. Hand movement: thumb control multi-function dial, index finger gently placed on the shutter to breathe evenly, just like pulling the bolt to achieve "intentional aiming, unintentional firing". At this time, the master has reached the realm of man-machine integration, and every ten steps will kill him! Of course, it is absolutely impossible not to shake. Even if you use Gitzo, it will at least vibrate at its natural frequency, depending on your requirements. The second introduction to digital photography, the accurate definition of exposure, if scientifically explained, is: the intensity of light multiplied by the time of light action. The "light intensity" in the definition refers to the intensity of light illuminating CCD, that is, illuminance (I stands for illuminance, in lux). The "exposure time" in the definition refers to the exposure time (t stands for exposure time, in seconds) when the photosensitive film is irradiated by Love rays. The unit of calculation of exposure is lux? 6? 1 sec. Taking e as the exposure amount, the exposure formula is as follows: e (exposure amount) = I (illuminance) ×T (exposure time), and the greater the light intensity, the shorter the exposure time; The smaller the light intensity, the longer the exposure time. If the light intensity is doubled, the exposure time needs to be reduced by half. If the light intensity is 2, the time is 4 and the exposure is 8; If the light intensity is 4 and the time is 2, the exposure is still 8. What is accurate exposure? In short, the meaning of correct exposure should be: let CCD receive the right amount of light at the right time. Speaking of exposure, I have to talk about Adams' regional exposure first. One of the greatest contributions of American photographer A. Adams, the master of landscape photography, to photography is to create the concept of "regional exposure". Anyway, I don't fully understand it myself. The theory in it is enough to write a book. But now my shooting is based on this part of understanding. Why can you see the changeable image geometry? Friends who have learned sketch will understand it easily. The picture is nothing more than a continuous transition from white highlights to saturated medium gray and then to all-black dark parts. This transition enables us to distinguish the outline of an object. The most traditional shooting technique is still the most effective in the digital field. When you see a picture, what do you want to show, that is to say, you want it to reflect the most saturated colors and the richest details. Just aim at it and test it, and then expose it according to the test value, and the resulting film will generally not let you down. Of course, if you want other parts to show a little detail, you must use reflectors and absorbers to control these places within the tolerance of your CCD, or change the angle and other light changes to reduce the light ratio. On the other hand, if you want to make a certain part appear pure black and white, and make these parts deviate from exposure value by more than five grades, you can see what you want to see. Understand the importance of point measurement and manual operation to the camera. Golden section COMPOSITION, the third introduction to digital photography, is a transliteration of English COMPOSITION and a term of plastic arts. "Composition" in Ci Hai refers to the arrangement and treatment of the relationship and position between people and things in a certain space by artists in order to express the theme and aesthetic effect of their works, and to form individual or partial images into an artistic whole. In China traditional painting, it is called "composition" or "layout". First of all, let's talk about the distribution and modeling in composition. I have to mention two nouns here: Jiugongge and Fun Center. Before the Jiugongge, let's talk about the famous golden section. In fact, the golden section is a division rule in plastic arts. Also known as the golden ratio, referred to as the golden ratio. Its division is to divide a straight line into two parts, so that the square of one part is equal to the product of another part and the whole, or the ratio of one part to the whole is equal to the ratio of the other part to this part. That is, the straight line segment AB is divided by point C, so that (AC) 2 = CB× AB, or AC: AB = CB: AC. Practice has proved that its ratio is about 1.6 18: 1 or 1: 0.6 18, which is called the golden ratio. The golden ratio was first discovered by the ancient Greeks. Until the19th century, it was considered by Europeans as the most beautiful and harmonious ratio. The golden ratio is widely used in plastic arts and has aesthetic value, especially in the aspect ratio design of arts and crafts and industrial design (such as book layout), so it is called the golden section. In the mid-20th century, French architect le corbusier discovered that the golden ratio has the nature of series. Combining with the human body size, he put forward the gold standard ruler scheme and used it as a measure of the beauty of modern architecture. France has also produced a group of cubist painters, called the golden section painting school, which pays attention to the proportion of forms. In fact, the golden ratio is only an approximation. The simplest method is to get the ratio of 2:3, 3: 5, 5: 8, 13, 2 1 as an approximation. This segmentation method is also used in optimization methods. It is found that the four points where the four lines of Jiugongge meet are the most sensitive places for human vision. In foreign photography theory, these four points are called "centers of interest". As the name implies, it has been repeatedly proved that when the subject is near or attached to these four points, it is easiest to get the "eyeball":) The fourth symmetrical balance of digital photography 1 echoes the horizontal position, so that the photographed image will not be skewed. You can use buildings, telephone poles and other objects parallel or vertical to the ground as reference objects, and try to keep the picture balanced when taking pictures. 2, good color balance, the picture should have a strong sense of hierarchy, to ensure that the main body can stand out from all backgrounds. Such as complementary color balance (below), the so-called red flowers and green leaves match this truth. With the same color balance, people wearing black clothes generally don't arrange to shoot on a dark background. 3. Foreground can balance the picture. Sometimes, when we find that the vacancy on the picture is unbalanced, such as when the sky in Wan Li is cloudless and monotonous, we put drooping branches and leaves on it to make up for the lack of the picture; Sometimes the bottom of the picture can't be pressed. When the top is heavy and the bottom is light, you can use rocks and railings as the foreground, and the dark color makes the picture feel depressed, achieving a stable and balanced effect. The foreground adopts the expression of virtual focus, which gives people a feeling of hazy beauty. 4. Blank. It is the link between objects on the communication screen and the relationship between them. Blank plays the same role in the picture as punctuation plays in the article, which can help the author express his feelings. Leaving a certain blank on the screen is the need to highlight the main body. To have visual impact, it is necessary to leave a certain gap around. This can be said to be a law of plastic arts. People need space to appreciate things. Exquisite works of art, if placed in a pile of messy objects, it is difficult to appreciate its beauty. Only when there is a certain space around, will it release its artistic light. If a picture is full of entities, it will give people a feeling of depression, and the blank space in the picture will leave people with room for manoeuvre. "If the painting is empty for three minutes, anger will follow." That's the truth. A, symmetrical composition, symmetry has always been emphasized by our nation, and it has always been a palace. The capitals are all symmetrically arranged. It emphasizes a solemn atmosphere, and a simple and solemn relationship is displayed in a "stable" symmetrical balance. B, the virtual and the real echo the layout, just like Jiangnan gardens. In some lyrical landscape pictures that emphasize elegance, quietness and softness, it is required that there can be sparse and dense, virtual and real in the changing balance picture, but overall balance is required. In an idyllic scene, such as a cow in the lower left corner and a cloud in the sky in the upper right corner, it would be better. The fifth line and triangle of the introduction to digital photography People often use a kind of "directional line cluster" in composition, which often receives the effect of "radiant". In most cases, the audience's eyes are directed to the main body, and its complete effect forms an atmosphere radiating outward from the main body along a straight line. This is a simple way to realize the visualization effect. Another basic skill of photographic composition is to use "internal lines" that can bring the audience into the picture. Although there are many complicated forms of lead-in, C-shaped, S-shaped and diagonal lines with perspective are the easiest to identify and succeed. "C-shaped line is also an effective lead-in, but when shooting, we should pay attention to the perspective line not to enter from any bottom corner bow. Generally speaking, the inner lead should not start from any angle, but from a measuring point slightly deviated from the center of the bottom edge. " As for the S-shaped line, some people call it "body line". This is a beautiful composition line first proposed by Huo Jiasi. Because it comes from the graceful figure of women: a slightly elongated "S" shape. As a common composition line, it can really impress people. The charm of S-shaped lines, when composing with lines, we should pay attention to one point, that is, the straight lines in the picture, especially the straight lines parallel to the picture, cannot extend from one side of the picture to the other without interruption. Otherwise, it is easy to have the following situation: the original intention is to take only one photo, and the result seems to be that two unrelated negatives are printed on one photo paper. This problem is most likely to occur when shooting natural scenery, such as the horizon in the middle and the sky and ground occupying half of the picture. If you still correct this problem? American photographer b? 6? 1 clements, D. Rosen and Field's book Photographic Composition pointed out that as long as "the continuity of this straight line is interrupted and the graphics of one part of the picture extend to another part of the picture, the overall sense of the photo is firmly established". Diagonal composition is a highly oriented picture. Using this composition is often the author's hope to draw the reader's attention to something obvious, or to show the charm of the line itself, because as we all know, the longest line in a rectangular picture is diagonal. Another common situation is that when two interesting centers are not obvious but need some connection, the author also needs a form to connect them. Look at the picture, it is a business card that reflects the grandeur of the bridge. The flashing bridge spans two corners and seems to be out of the picture. Unstable triangle composition can enliven the picture, which is often used in changeable women. The picture below is an example. Of course, this composition can also be used to render unstable and irritable emotions, but I haven't found a suitable picture to demonstrate. The seventh entry of digital photography is the art of running out of light. To put it bluntly, playing photography is playing with light. Just like sketch, the expressive force of light is the "soul" of a good PP. Let's discuss several concepts first: any kind of light has three elements, namely intensity, direction and hue. Light intensity describes the intensity of light, and the light emitted by various light sources has a certain intensity. Strong and direct light can cause obvious shadows and clearly present the outline of the object, so it is often used to outline the outline of the object; Strong light can also increase the brightness and color contrast of the subject. Weak light and scattered light can weaken the contrast between light and shade of the subject and make the surface of the object look smooth and detailed. For camera lighting, in the studio, strong light source is often used as the main light, which is the main source of shooting lighting. The weak light source should be used as auxiliary light, which can weaken the strong shadow caused by the main light, and at the same time, it will not cast unnecessary shadows. But if the light is too strong, it often can't achieve good results, because the shadows formed under strong light will be exaggerated and the lighting effect will be unnatural. When shooting, if the light is too strong, you can reduce the intensity of the light by installing a diffusion screen or a reflector. Compared with strong light, the light and shadow effect of astigmatism is softer and more natural. The light receiving surface of the main body can be uniform, the contrast is moderate, and the directivity of the light source is limited. Another kind of light is the so-called "diffuse light". There is no obvious directional light on cloudy days, which is called diffuse light. Different from the two light sources mentioned above, diffused light has almost no shadow, and the famous photographer Bresson is a master of controlling diffused light. Eight intensity of illumination Introduction to digital photography, commonly known as lux, indicates the luminous flux per unit area of the surface of the object being photographed. 65,438+0 lux is equivalent to 65,438+0 lumens/square meter, that is, the luminous flux vertically irradiated by a light source with luminous intensity of 65,438+0 Candeira at a distance of one meter per square meter from the subject. Illuminance is an important index to measure the shooting environment. When the sunshine is strongest at noon in summer, the outdoor illumination can reach more than 100000 lux, which is easy to form obvious shadows and may not be an ideal shooting environment. Most indoor illuminance is below 300lux. Illumination is not only related to the luminous intensity of the light source, but also related to the distance from the light source to the object being photographed. Generally speaking, when the distance between the subject and the light source is constant, the illumination of the subject is directly proportional to the luminous intensity of the light source; On the contrary, when the luminous intensity of the light source is unchanged, but the distance from the object changes, the illuminance on the object is roughly inversely proportional to the square of the distance. The aperture change when using a flash is based on this principle. There is also a rule: when a light source illuminates the subjects before and after, the closer the light source is, the greater the illumination difference between the two subjects; The farther the light source is, the closer the two objects receive light. This change has applied different contrasts in the last issue of "composition", which will cause a very strong visual impact. Having said that, I hope you will not be confused with the concepts mentioned in the last issue. In the last issue, we talked about the directionality of light, and illuminance refers to intensity. The two are quite related, but there are differences. Strong light is easier to get directionality, but if the room is full of strong light in this direction, pp will run out of direction. For example, under the macro ring flash, all shadows are "eliminated". What is the direction at this time? On the contrary, the portrait by the window, although the indoor lighting is quite weak, is highly directional, and is often used to depict the stability and reserve of adults. The concept that all light has directionality is easy to understand. According to the relative position of light source, object and camera in the horizontal direction, light can be divided into three basic types: forward light, backward light and lateral light. According to its longitudinal relative position, it can be divided into four kinds of lights: top light, top light, flat light and upward light ... The direction of light in the ninth lecture of Introduction to Digital Photography is now classified in detail. The concept that all light has directionality is easy to understand. According to the relative position of light source, object and camera in the horizontal direction, light can be divided into three basic types: forward light, backward light and lateral light. According to its longitudinal relative position, it can be divided into top light, top light, flat light and glazing. 1, the front camera and the light source are in the same direction, facing the subject, so that the surface facing the camera can easily get enough light, which can make the subject clearer. According to different angles of light, fairing can be divided into front fairing and side fairing. Forward light is the light that directly shines on the subject along the direction of the lens. If the light source and the camera are at the same height, all the parts facing the camera lens can receive light, so there is no shadow. The image taken by such light will reduce the contrast of the subject and lack the three-dimensional sense like a plan. Shooting in such light will often lead to unsatisfactory results, which will make the subject lose its original light and shade level. I won't give the picture here. Most of the photos illuminated by airborne flashlights are of this light. Side light refers to the light from the left or right side of the camera to the subject. When shooting, side light is the ideal light for shooting with a single light source. In most cases, 25 ~ 45 side light is generally used for lighting, that is, the included angle formed by the connecting line between the camera and the subject and the connecting line between the light source and the subject is 25 ~ 45. At this time, the part of the subject facing the camera is illuminated, and partial projection appears. This can better express the facial expression and skin texture of the characters. It not only ensures the brightness of the subject, but also makes the contrast between light and dark appropriate and stereoscopic. Most of the "beautiful" photos in Taiwan Province photo studio were taken in this light. 2. Side light The light source of side light is the light that shines on the subject from one side of the straight line formed by the camera and the subject. At this time, half of the front of the subject is illuminated by light, and the shadow is slender, the projection is obvious, and the three-dimensional sense is strong, which can show the grandeur of the building. However, due to the strong contrast between light and shade, it is not suitable for expressing the delicate texture of the subject. However, in many cases, this photometry can well express the texture of rough surfaces. 3. Top light, top light and top light usually describe the outline of the upper part of a person or thing, which is isolated from the background. However, when the light shines above the subject from above, it will make the scene flat, lack of layering and poor color effect. This kind of lamp is seldom used. Especially in the photos of people who "visit here", the light at noon often causes extremely heavy shadows under the nose and under the bags under the eyes, which is very ugly, so it needs to appear on the surface. Of course, under special circumstances, the dome light is used well, and there are also successful examples. The dome light is the most used of these three kinds of lights. In general lighting, when dealing with the main light, the light source is generally arranged slightly higher than the main body and forms an angle of 30 ~ 45 with the ground. This kind of light can not only make the front of the subject get enough light, but also have a three-dimensional effect, and the shadow formed will not be too obvious. However, this kind of lamp is rarely used alone, but it is mixed with other auxiliary lights in the studio, such as side lights, which will produce good results. Still no pictures, everyone took out their wedding dresses, many of which are widely used.