What part of the camera measures light and distance?

Most digital cameras or traditional point-and-shoot cameras have several metering methods: central average metering, central partial metering, spot metering and evaluative metering. These light metering methods can basically cope with all current shootings, but in photo studios and some professional occasions or advertising shootings, photographers still rely on the value of the light meter for shooting.

1. Center-weighted average metering (or simply: center average metering)

Central average metering is the most commonly used metering mode, and is used by almost all camera manufacturers. All use central average metering as the camera's default metering method. Central average metering is mainly based on the fact that ordinary photographers are accustomed to placing the subject, that is, the thing that needs to be accurately exposed, in the middle of the viewfinder, so this part of the shooting content is the most important. Therefore, the sensory element responsible for metering will organically separate the overall metering value of the camera. The metering data in the central part occupies the vast majority of the proportion, while the metering data outside the center of the screen serves as a small proportion and plays an auxiliary role in metering. . After the camera's processor weights the average of the two grid values, the camera metering data is obtained. For example, Nikon cameras use center-weighted average metering. The central part of Nikon cameras accounts for 75% of the entire metering ratio (this ratio varies among brands), and the other non-central parts gradually extend to the edges. Photometric data accounts for 25%. Center-weighted metering is a very practical and most widely used metering mode in most shooting situations. However, if the subject you need to shoot is not in the center of the frame or you are shooting under backlight conditions, center-weighted metering will not work. Applied.

Center-weighted metering is a traditional metering method. The metering algorithm of most cameras focuses on about 2/3 of the center of the frame, and also takes some degree of consideration into the surrounding areas. For photographers who are accustomed to using center-weighted metering, it is easier to control the effect of metering in this way than using multi-zone evaluative metering.

Applicable shooting purposes: personal travel photos, special scenery photos, etc.

2. Central partial metering (or partial metering)

Central partial metering and central average metering are two different metering methods. Central average metering It is a metering method that uses the central area as the main area and other areas as auxiliary. Central partial metering only measures the area in the center of the screen. The metering range is about 3% to 12%. Light. The central partial metering mode is suitable for some scenes with more complex lighting. At this time, more accurate exposure is needed. Using the central partial metering can get photos with accurate exposure of the subject. Central partial metering can be used in some special harsh shooting environments, which can ensure that the camera processor calculates the exposure required for the main part of the subject in the center of the frame. This mode is most suitable in scenes such as stages, performances, and backlighting. However, due to the rise of split metering (matrix metering) mode, this mode has gradually become less common in cameras. Canon is a manufacturer that insists on using central partial metering (local metering). The latest EOS 30V film camera and EOS 20D digital SLR camera are designed with 9% area range of local metering, which can make no point Cameras with metering function can reduce the impact of light on the subject when shooting pictures under complex lighting conditions.

Partial metering is to meter a certain part of the screen. When there is a strong contrast between the light and dark between the subject and the background, and the subject occupies a small proportion of the frame, this metering method is most suitable; in this case, local metering is better than the first and second metering methods. It is accurate, and unlike the spot metering method, the metering point is too narrow and requires certain metering experience to prevent errors.

Applicable shooting purposes: when accurate metering is required under specific conditions and the metering range is larger than spot metering.

3. Spot metering (SPOT)

Although central average metering (center-weighted average metering) can fully express the light response of the entire screen, it also has many shortcomings. For example, when accurate exposure of a small-scale object is required, central average metering (center-weighted average metering) is not so easy to use. Even central partial metering (partial metering) sometimes has a large range. In order to overcome these shortcomings, some manufacturers have developed this spot (SPOT) metering mode to avoid the influence of ambient light sources on subject metering under complex lighting conditions or backlighting conditions; the range of spot metering is based on the center of the viewing window. A very small area is used as the exposure reference point. The metering area of ??most spot measurement cameras is one to three percent. The camera uses the light measured in this narrow area as the basis for exposure. This is a very accurate metering method, but for novices, it is not easy to master. How to distinguish a metering point has become a skill that needs to be learned. The picture taken by the wrong metering point Either overexposed or underexposed, causing serious exposure errors. Due to the spot metering technique, it can also be used to shine in the increasingly popular macro photography of digital cameras, which can make the exposure of the macro part more accurate. Therefore, those who like macro photography must try their best to learn this metering method. Initially, they can choose a small area in the middle of the picture as the metering reference point. Spot metering is also a good weapon when shooting portraits, which can accurately expose parts of the person (such as the face, or even the eyes).