Photometric measurement

This is a moderate metering method, which takes into account the overall brightness within the framing range and the fact that the subject is generally located in the central area when shooting, so it is suitable for occasions where the subject is prominent and the background needs to be taken into account. \x0d spot metering is a professional metering method, which takes the area in the center of the picture as the metering area. This is an extreme metering method, which is suitable for situations where the light is complex or the light ratio is strong and it is necessary to highlight the subject. Create a special artistic effect. \x0d central focus photometry \x0d central focus photometry refers to photometry focusing in two semi-arc enclosed areas in the view frame. The camera is set to spot metering mode, and the metering point is the focus. There are two situations at this time. When the focus mode is not point focus, the camera will measure the light spot from the center to the focus; When the camera is set to point focus mode, the camera will measure the light spot according to the selected focus. \x0d All objects reflect light (objects that never reflect may be called blackbody), and objects that do not reflect do not exist on the earth's surface (whether the center of the earth exists, I don't know). The principle of spot measurement is to analyze a certain point with an optical sensor. Measure the reflectivity of an object (usually a subject). Convert the light intensity signal into an electrical signal. This is automatic metering. \x0d Scientists found that the reflected light with high reflectivity (high tone), medium reflectivity (gray tone) and low reflectivity (low tone) is usually 18% reflectivity (medium gray tone). The metering system of the camera is based on the gray scale of 18%. If the reflectivity exceeds 18%, it is considered that the camera is overexposed and needs to be reduced (reducing the aperture or adjusting the shutter), otherwise it is underexposed and needs to be increased.

How to use several metering methods of the camera correctly?

Now SLR cameras and digital cameras basically have the following three metering modes:

1. average photometry: calculate the average photometry value of the whole scenic spot.

This is the default basic metering mode of general cameras, and the usage rate is the most common. You can almost take a satisfactory photo when the light is even and the contrast between light and dark is not great within the range of view.

2. Center average photometry: calculate the photometry value of 10-30% framing range.

When the subject to be represented is in the middle part of the framing range, and the ambient light and shade are quite different from the subject, the center average metering is selected, and only most central areas are metered, which can make the exposure of the subject more accurate.

3. Spot metering: also known as key metering, it is metering in the area of 1%-5% within the framing range.

Spot metering mode is rarely used and is not easy to master. But in some cases, spot metering can play an important role. Knowing when spot metering should be used and using spot metering correctly can make the exposure of the subject accurate on the one hand, and create wonderful pictures that can't be seen in reality by using "sensitivity tolerance" on the other hand.

What does SLR metering mean and how to operate it?

"Metering is an important function of SLR cameras. Photometry is whether the degree of light passing through the lens is suitable for the camera to make corresponding prompts.

Generally divided into spot metering, center average metering and average metering (also called distance metering).

1, spot metering is focusing spot metering, which is to measure whether the light at this point you want to focus is appropriate, such as shooting people's faces and flowers, and so on.

2. Central average photometry is to measure the light around the focus, such as shooting some large objects;

3. Average photometry is used for more scenes so that the whole phase will not be too exposed.

Photometry is generally practiced, and how to use it is according to your own needs. If you take photos with the wrong metering, it won't work. This is like shooting a person's face with average photometry. The hair is black, which will cause the face to be too exposed, that is, the face is white. Practice slowly, which is also the fun of photography. "

What are the three metering modes that come with a general camera?

1. Spot metering mode: the metering element only measures a small range in the center of the picture.

This metering mode is mostly used when the photographer wants to fully express the subject. When shooting, the camera lens is aimed at various parts of the subject many times and its brightness is measured one by one. Finally, the photographer determines the exposure parameters according to the measured data. For example, when shooting people in a studio with uniform light, many photographers will adopt spot metering mode to measure the key parts of the people, such as eyes, face or distinctive clothes and limbs, and focus on their distinctive parts to achieve the artistic effect of highlighting the theme.

2. Central part metering mode: This mode is to meter the area in the center of the picture that accounts for about 12% of the picture.

In fact, this metering mode is an extension of the central point metering mode. The photometry element of the camera will photometry the area where the center of the picture accounts for about 12% of the picture, and finally get photometry data through average weighting. This metering mode is very suitable for shooting various subjects in the center of the picture or landscape photos with little contrast of ambient light.

3. Center focus average metering mode (full metering): This mode focuses on the center of the picture (about 60% of the picture), taking into account the edge of the picture, which can greatly reduce the phenomenon of poor exposure of the picture, and is the default metering mode of digital cameras.

Generally speaking, when using this mode to measure light, the camera will focus on the center of the picture (about 60% of the picture), taking into account the edge of the picture. At present, many digital cameras will have this metering mode. When using this metering mode, when Gao Fancha or different colors appear in the picture, the camera will meter several areas, focus on a certain area according to the photographer's needs, and then carry out weighted average. The image obtained in this way rarely has the problem of underexposure or overexposure in a certain area, but for some key subject parts, the image can be clearly reflected, so it is very suitable.

What kind of metering method does SLR camera use? How to measure light and how to expose it correctly.

Hello!

See "Which metering mode to use under what circumstances".

I. Evaluation measurement (multiple measurement):

When shooting, the camera divides the image into several areas for photometry, and then calculates the most appropriate average exposure required for the whole picture to ensure accurate exposure. The average metering mode is mainly suitable for objects with no strong contrast between the shooting object and the background, and the brightness difference is relatively flat. Multi-zone evaluation photometry is the most advanced intelligent photometry method at present, and it is a kind of judgment that simulates the uniform or uneven illumination that the human brain often encounters when shooting. Even people who are not familiar with photometry can generally get films with more accurate exposure in this way.

Applicable environment: group photos, family photos and general scenery photos.

Second, the central key average measurement (part of the central measurement)

Average the photometry of the whole image, but focus slightly on the central object. The central focus average metering mode is a very reliable metering mode, which is suitable for almost all subjects. To sum up, it is necessary to choose the central average metering system to shoot the content that needs to show the main body, and at the same time take into account the overall exposure.

Application environment: personal photos, special scenery photos.

Three, the center point measurement (that is, "fixed point measurement"):

Spot photometry can only accurately measure the light in a small area, and the brightness of the scenery outside the area has no influence on photometry, so the photometry accuracy is very high, and its main purpose is to measure the light in a specific small area in the distance.

If the contrast between the subject and the background is relatively large, you can consider spot metering, such as backlight.

Application environment: stage photography, personal art photos, special story photos, etc.

Different metering modes lead to different imaging effects. Not every photo can strictly adjust the metering mode, and it is possible that the beauty will disappear in the blink of an eye when you adjust it. However, some photos also need to adjust the metering mode, otherwise it will be a mess, and we must learn to master and use it flexibly in practice.

What are photography and photometry for?

The metering system of digital camera generally measures the brightness of the reflected light of the subject, which is also called reflection metering. According to the different placement positions of metering elements, metering methods can generally be divided into external metering and internal metering. (l) External metering: In the external metering mode, the optical paths of the metering element and the lens are independent. This metering method is widely used in head-up viewfinder shutter cameras with sufficient sensitivity and accuracy. Single-lens reflex cameras generally do not use this metering method. (2) Internal metering: This metering method is based on the lens and is called TTL metering, which is consistent with the shooting conditions and can be automatically corrected when changing the phase lens, changing the shooting distance or adding a color filter. At present, almost all single-lens reflex cameras adopt this metering method.

In fact, the principle is very simple. The camera automatically assumes that the reflectivity of the measured area is 18%, and then determines the values of aperture and shutter through this ratio. Aperture and shutter are related. Under the same lighting conditions, the larger the aperture value, the smaller the shutter value, and the smaller the aperture value, the larger the shutter value. The numerical source of 18% depends on the reflective performance of middle tones (gray tones) in natural scenery. If there are many white tones in the framing picture, the reflected light will exceed 18%. If it is an all-white scene, it can reflect about 90% of the incident light, while if it is a black scene, the reflectivity may be only a few percent. The standard grey card is an 8* 10 inch card. If this gray card is placed under the same measuring light source of the subject, the overall reflectivity of the measuring area will be standard 18%. Then, as long as you shoot according to the aperture shutter value given by the camera, the photo will be exposed accurately. If the overall reflectivity of the whole metering area is greater than 18%, as we said above, the background is dominated by white tones. At this time, if you shoot according to the aperture shutter value determined by the camera's automatic metering, the photo you get will be an underexposed photo with a gray white background. If it is white paper, it will become black paper. Therefore, shooting scenes with reflectivity greater than 18% needs to increase the EV exposure compensation value of the camera, and the specific compensation EV value needs to be analyzed according to the specific situation. At this time, experience is very important. On the other hand, if you shoot a scene with a reflectivity lower than 18%, such as a black background, your photos will often be overexposed and the black background will turn gray. Therefore, shooting scenes with reflectivity below 18% needs to reduce EV exposure, which is the principle of "white plus black minus".

Hope and answer are helpful to you.

How to select metering mode in camera settings

Due to the different metering methods used in different environments, we need to choose the appropriate exposure method. In the previous course, we have mentioned the basic settings of the camera, so today we will mainly explain several metering methods in the camera settings: central key metering, partial metering, spot metering and evaluation metering (matrix metering). First, central key metering (or simply: central average metering) is the most widely used metering mode, and almost all camera manufacturers use central key metering as the default metering method for cameras. Center-focused photometry mainly considers that the subject is usually arranged at a lower position in the center of the picture in general photographic composition, so this photometry method takes into account both the environment and the subject, making the measurement more reasonable. In most shooting situations, central focus metering is a very practical and widely used metering mode, but it is not applicable if the subject you need to shoot is not in the center of the picture or under backlight conditions. Central focus photometry is a traditional photometry method. Most camera metering algorithms pay attention to about 2/3 of the center of the picture, and consider the periphery. For photographers who are used to using central focus metering, it is easier to control the effect by using this metering method than by using multi-zone evaluation metering method. The central key photometry has a wide application range, considering both the subject and the environment, and is suitable for use in various environments. For example, this metering method is often used when shooting portraits in tourist areas, and central focusing metering is not suitable for use in the case of large contrast of scenery. Second, partial metering partial metering and central focus photometry are two different photometry methods. Central focus photometry mainly focuses on the central area, supplemented by other areas. partial metering only measures one area of the picture, and the photometric range is about 3% to 12%. Partial metering mode is suitable for some scenes with complex light, and more accurate exposure is needed at this time. Partial photometry can be used to obtain photos with accurate exposure of the subject. The central part photometry can be applied to some special harsh shooting environments, which can further ensure that the camera processor can calculate the exposure required for the main object part in the center of the picture. For example, this mode is most suitable for scenes with complex lighting such as stage, performance and backlight, and can reduce the influence of light on the subject when shooting pictures with complex lighting conditions.

When the contrast between the subject and the surrounding environment is strong, the light is complex, and the proportion of the subject in the picture is not large, this metering method is the most suitable; Suitable for shooting purposes: accurate metering is needed under certain conditions, and the metering range is larger than that of spot metering. Third, spot metering

Although central focus photometry can fully show the light response of the whole picture, it also has many shortcomings. For example, it is not so good when a small range of objects need to be accurately exposed. Then the range of spot metering mode takes a small area in the center of the viewfinder as the exposure reference point, and the metering area of most point cameras is 1% to 3%. The camera uses the light measured in this narrow area as the exposure basis.

Spot metering mode is mostly used when the photographer wants to fully express the subject. For example, when shooting people in a studio with uniform light, many photographers will adopt spot metering mode to measure the key parts of the people, such as eyes, face or distinctive clothes and limbs, and focus on their distinctive parts to achieve the artistic effect of highlighting the theme.

Spot metering can accurately expose parts of people (such as faces and even eyes) when shooting portraits.

Spot metering is often used when taking portraits, macro photos and other photos that need to highlight the subject, which is suitable for shooting purposes: stage photography, personal art photos, close-up story photos and so on. 4. Evaluation photometry (matrix photometry) Evaluation photometry is a relatively new photometry technology, and the biggest difference between evaluation photometry and central key photometry is that evaluation photometry is to divide the framing picture into several photometry areas, and then carry out integral weighting on each area to calculate an overall exposure value. In fact, the essence of this metering method is to divide the whole picture into multiple areas, and then use independent metering elements to measure the light, and then the microprocessor inside the camera processes the data to get the appropriate exposure. This mode is more suitable for photos of big scenes, such as scenery and group photos. The effect is best when shooting scenes with relatively positive light sources and uniform illumination. At present, it has become the most commonly used metering method for many photographers and photographers.

Because the photographer used the evaluation metering mode and set the correct combination of aperture and shutter, the brightness of the sky, people and the ground can be properly expressed.

Suitable for shooting purposes: group photos, family photos, general scenery photos, etc.

The above introduces the principle of photometry and several common photometry methods, hoping to bring help to everyone in actual shooting. In fact, no matter which metering method is adopted, it needs to be carried out according to the actual needs of the photographer. In photography, whenever we want to shoot, we must clearly understand what we want to shoot, as long as we grasp what we need to shoot, that is to say, we must be clear about the subject to shoot. When the subject is relatively single, we can use the method of point and partial photometry to measure light, while if we shoot some scattered subjects such as scenery, we can use evaluation photometry or center key average photometry. Generally speaking, if you really want to skillfully use the metering system of a digital camera to expose the subject correctly, you must pay more attention to observing the ambient light and estimate the relationship between the tone of the subject and the contrast of the environment when shooting. Finally, according to your own needs, adjust the aperture and shutter appropriately and adjust the light to achieve your own satisfactory results.