Use of Exposure Compensation

The digital camera is easy to use. After shooting, you can immediately know the actual shooting effect through playback. In addition, you can adjust the contrast color on your computer later, therefore, many photographers do not pay much attention to the accuracy of the exposure in practice. In fact, the exposure requirements for digital cameras are also very high. In practice, they must pay special attention to the use of "Exposure compensation, when shooting some special objects, we should also use our accumulated experience in traditional photography to make full use of exposure compensation to meet the exposure needs in specific situations and ensure accurate exposure photos.

1. Why is exposure compensation required?

Like traditional cameras, the metering and exposure system of digital cameras has a basic principle in image processing, that is, to restore all the subjects according to the Neutral gray brightness of 18%, therefore, in the camera's photosensitive system, regardless of the original brightness, the final display should be in a moderate brightness. Therefore, in actual shooting, the photographer still needs to make a judgment based on the complex conditions of the shooting scene. Only in this way can the photographer ensure the desired density and color reproduction.

Generally, most portable digital cameras have positive and negative 2-screen exposure compensation, which can be used to cope with shooting needs in most complex situations. For some advanced single-lens reflective digital-code cameras, the exposure compensation even reaches the plus or minus 5 blocks, which can meet the shooting needs in extremely complex lighting environments. The reason why digital cameras are designed and manufactured to deal with the camera in this way is that the exposure compensation is of great significance to the photo quality and is a key technical point that cannot be ignored. In general, whether exposure compensation is required or not, photographers must consider the following aspects.

2. When the brightness of the object to be taken is high, positive exposure compensation is required.

For example, when shooting wind light, if the blue sky, white clouds, and other light-colored content occupy a large area, we should consider increasing the exposure volume as appropriate, and adding at least half a block to the light, and adding one block to the side. If it is against the light, it is necessary to deal with the location of Taiyang, while looking at what you are doing, usually you want to show the details of the screen can also be appropriate, we need to increase the exposure by 1.5-2 blocks. The more the sun is in the center of the screen, the more exposure needs to be increased. (Of course, we should also pay attention to avoiding the sun with strong light, prevent Damage to camera image sensors. If the sun does not emit strong light, such as the red sun in the fog and the sunset, the exposure compensation issue does not need to be considered because they have low brightness and will not affect the light measurement ).

In addition, when shooting specific content such as snow scenes and fog scenes, you must make exposure compensation as appropriate based on the characteristics of the presentation objects in a high-profile form. Generally, it is best to compensate for the first-to-second half-exposure when shooting a snow scene. Otherwise, the final snow you get is not white, and may become gray due to insufficient exposure; it is best to compensate for the impression of the first block when shooting the fog scene. Otherwise, the shadow tone you get is dark, close to the night scene, which is obviously not ideal.

When there are people who wear white clothing in groups, hospitals or laboratories with high ambient brightness, large areas of airplanes with sky as the background, and other special objects, make appropriate positive exposure compensation based on the relationship between the subject and the background.

3. When the brightness of the subject is low, Negative Exposure compensation is required.

When processing high-brightness shooting objects, you need to make positive compensation for the exposure, mainly to prevent the camera from Automatically Processing the image as an undershot. In the same way, to take a deep-tone object, you need to do the opposite to avoid excessive exposure.

Typically, when shooting night scenes of a city, in addition to the main area occupied by buildings, streets, or other high-brightness content on the screen, it mainly relies on two methods to prevent excessive exposure, one is to use the spot test to measure the light exposure of the main display objects; the other is to use the exposure compensation to reduce the exposure according to the actual situation. Generally, when a large area of the sky is occupied by images (especially the sensitive parts of the light in the middle of the screen), two or more exposures are required.

In addition to shooting night views, you must take appropriate measures to reduce the exposure by taking advantage of negative compensation for the exposure of mountains in dense summer shade and back-to-light. In addition, shooting of figures in black clothing, shooting of textiles in deep tones, and so on, all of which need to reduce the exposure volume to make it possible to get a normal effect. Because the digital camera also determines the exposure by measuring the reflected light of the object to be taken. If the photographer does not make Negative Exposure compensation when dealing with objects with low brightness, the final result is a neutral gray tone. Obviously, it is very unacceptable to convert a shooting object that is obviously Black or deep into a neutral gray-based image.

4. flexible handling of the complex relationship between the subject and the background

There are two main situations: A. High Background Brightness, low subject brightness, and positive exposure compensation. This situation often occurs when shooting meeting characters. Sometimes the characters sit in front of the window, while there is sunlight on the back of the window. The background is bright and the characters are obviously dark, in this case, if you do not use the flashlight to make up the light, you need to make positive compensation for the exposure. Generally, you need to increase the exposure compensation by about 1 block, and the facial level of the person will be significantly improved. In addition, when shooting a reversed portrait, if the background includes a large area of the sky, the water surface and other high-brightness objects, the contrast should also be improved through positive compensation or other forms of auxiliary light, otherwise, it will affect the reflection of the subject. Even if you use image processing software to highlight a person, the image quality will be significantly affected by the noise.

B. The Background Brightness is low and the subject brightness is high. Negative Exposure compensation is required. This situation is often encountered in stage photography. When one or a few actors perform on the stage, in order to attract the attention of the audience, they often use one or two high-performance lights to shine on the characters, at this time, the other backgrounds on the stage are almost black because they are not directly exposed to light, so the two are in a great contrast, unless the performer is in the center of the screen and you have adopted the spot metering mode, otherwise, Negative Exposure compensation must be made; otherwise, excessive exposure may occur.