How to control exposure in backlight photography

Backlight and side backlight photography can best express the outline and three-dimensional shape of the subject, and have a strong sense of depth. Therefore, in the process of photographic modeling, backlight and side backlight are very expressive. It can show a bright outline and highlight the three-dimensional modeling of the subject, which is determined by the direction of illumination. Backlight and side backlight can only illuminate the edge of the outline of the scene, so it will naturally present a bright outline, make the slightly convex part brighter, and make the slightly concave part form a shadow, so it can best show the ups and downs and texture of the subject. The reason why it can show a strong spatial depth is that the particles scattered in space scatter light, and the particles themselves have a certain brightness. Particles in the air include water vapor and dust. These particles are illuminated by light, and their scattered or diffused light is not easy to be detected. It is more obvious when backlight and side backlight are used, and the film itself is sensitive to the blue-violet light of short-wave light, so the brightness will increase. This extra brightness will naturally make the foreground appear brighter, and the farther away it is, the brighter it will be. This feature accords with the feeling of human eyes when observing the distant view, so the backlight and side backlight can best show the deep spatial effect. Photographic exposure under side backlight conditions should distinguish several different situations. Different methods of measuring and fixing light are adopted. 1. Photometry under backlight means that the subject under backlight is full or mostly full of the picture range, and there are no large bright objects in the picture. Such as trees, foothills and overhead ground scenes under backlight. In this case, if the camera used is an exposure meter directly measured through the lens, it can be directly measured and corrected on the basis of measurement. When correcting, we should analyze the proportion of light and dark scenes in the picture, and compensate the first-order aperture on the basis of the original photometry according to the different proportion relationship between less bright and darker scenes to determine the appropriate exposure combination. If there is no internal exposure meter, it can be modified by using the photometric principle of forward photography. However, attention should be paid to prevent the direct light of the sun from directly projecting on the photovoltaic cell in order to show the tone characteristics and rich colors under backlight illumination. 2. Open scenery under backlight When the area of the sky accounts for about one-third of the picture and under backlight, it can be directly exposed according to the data indicated by the central key photometry and exposure meter in the camera, because it focuses on measuring the center or lower part of the picture and is suitable for shooting such scenes. If there is no metering device in the machine, you can use a hand-held exposure meter. When measuring light, the exposure meter should be slightly inclined to the ground to measure light, so as to be less affected by the bright tone of the sky, resulting in underexposure of the ground scenery. 3. Backlight scenes with dark foreground Some scenes under backlight illumination, and the obvious part of the picture has extremely dark foreground. At this time, if the internal exposure meter is organic, it cannot be exposed directly according to the value indicated by the lens metering system. Because there is little reflected light in the dark foreground of a large area, the brightness measured by the exposure meter will be obviously low, which will lead to overexposure in the middle and long range. In this case, you should only aim at bright medium and long-range overexposure. In this case, you should only aim at bright mid-distance and long-distance measurements. Photographers who do not have a built-in metering system should also aim at the subject with an exposure meter, determine the exposure according to its brightness value, and regard the dark foreground as a silhouette or semi-silhouette effect. 4. Exposure control of the water surface with halo. The water surface with backlight often reflects bright halo, while the subject is in the shadow, and the brightness distribution is very uneven, which makes it difficult for us to determine how to use the exposure meter to measure light. In this case, the exposure should be less than or greater than, because the reflection of water flare is very strong and the brightness is very high. If the exposure is slightly overexposed, the detail level of the light spot will be obviously lost and the texture will be improved seriously. In this case, according to the brightness exposure, the dark scene should be properly considered and the dark part should be regarded as a semi-silhouette effect. 5. Still-life shooting with side backlight tends to show their three-dimensional sense and texture. At this time, the front of the illuminated still life presents a large area of dark tone, and the bright side produced by side backlight illumination only accounts for a small area. In this case, the exposure meter should be used to measure the dark brightness of the surface of the still object, and then the half-step or one-step aperture exposure should be appropriately reduced according to the indicated reading. In this way, we can reproduce the appropriate tone points under the side backlight illumination, and directly expose the dark parts according to the readings, which will inevitably reproduce the medium brightness, thus destroying the original tone effect. In the long-term photographic practice, photographers should be good at accumulating photographic exposure experience, mastering the brightness distribution under different lighting conditions and analyzing the brightness value of correct exposure. The exposure of the brightness of various scenes mentioned below is carried out with measuring tools. However, there are often some special circumstances in photography, which cannot be measured by photometry. At this time, we need to rely on our usual accumulated exposure experience and comprehensively analyze the brightness of various scenes to determine the correct exposure combination, so as to better ensure the technical quality of the picture. For example, in news photography, because the scene of the subject changes greatly, the lighting conditions can not be fixed, especially for the subject with strong timeliness, and photographers are often not allowed to measure the brightness of each scene in many occasions. In this case, it is necessary to rely on the usual accumulated exposure experience to determine the exposure. The accumulation of these experiences can not be achieved in a few days, but in the long-term photography practice, we can analyze and summarize the brightness of various scenes in order to form some regular things. There are two methods to accumulate exposure experience and estimate exposure: the change of indoor and outdoor scene brightness. In location photography, to fully estimate the change of natural lighting, pay attention to the following factors. The change of the incident angle of the sun in a day, the change of the direction of illumination received by the scene, the change of the intensity of reflected light from various scenes under the same illumination, and the change of weather, altitude, latitude and season directly affect the exposure control. However, if the photographer grasps the changing law between them, it is easy to make correct judgments in various situations. In photography, we should pay attention to summing up the exposure experience through concrete practice under various conditions. Only by repeating this exercise can we find a way to control the exposure. Indoor light changes are more complicated than outdoor ones, because the shooting contents are different, the scenes are different, the rooms are large and small, and the reflectivity of indoor scenery is different. More importantly, the size and amount of room windows will affect the exposure, plus the changes of outdoor natural light (cloudy days, sunny days, sun incident angle, seasonal changes) and other factors, which should be considered when estimating the exposure; At the same time, it also includes the brightness change of indoor lighting, the distance between the shooting scene and the light source, the direction of illumination, the intensity of illumination, the luminous efficiency of lamps and so on. Mastering these brightness changes is the same as the above method, which requires repeated practice, careful observation and diligent thinking. Lighting conditions under different conditions are used in photography practice. In this way, we can find out the scene brightness suitable for this theme under various complicated lighting conditions, as the basis for determining the exposure combination, realize our shooting intention and complete the artistic modeling of the picture.