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First of all, let's introduce what photometry is. Whether in full automatic mode, aperture priority mode or shutter priority mode, the camera can always automatically generate a set of exposure parameters (F\ S\ ISO) when taking pictures, and the exposure of the photos is normal, which is calculated by the camera after photometry.

Don't say "I didn't measure the light". Photometry is a necessary work before the camera takes a picture. The camera must measure the light before you press the shutter.

Cameras generally have four photometric modes, each of which will produce different results, which will affect the appearance of the photo. Which photometric mode should be chosen when taking pictures?

(1) photometric mode 1. Evaluation photometry is the name of Canon, other brands of cameras also have average photometry, matrix photometry, multiple photometry and so on, are all the same thing. When evaluating photometry, the camera will evaluate the picture as a whole and generate a set of exposure parameters to ensure that the exposure of the picture is normal.

The evaluation photometry is suitable for the case of global average brightness, the brightness transition is uniform, there is no large light ratio, and the light-dark contrast is small. For example, in the smooth light, the brightness of all objects is the same, and the accurate exposure can be obtained by using evaluation photometry.

two。 The local photometric camera only measures the area in the center of the picture, regardless of the edge of the picture. When the center of the picture is the subject we want to shoot, and the brightness difference between the middle part and the edge is too big, we can use local photometry.

3. If you look at the name of the central focus on average photometry, you will know that it not only has the function of average photometry, but also takes into account the method of local photometry. In this metering mode, the camera gives priority to the central area of the picture, but also takes into account the edge area (unlike local metering), but still focuses on the central part.

4. Spot light only measures light at one point in the picture, except for this point, I don't care about anything else. The metering area is very small, some cameras are in the middle position, some cameras have linkage function, and the focus is the metering point. Spot light measurement is generally suitable for high light ratio environment when backlighting.

The results of different areas of the screen selected by point photometry

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(2) choose the appropriate photometric mode according to different scenes, we can choose the appropriate photometric mode.

For example, I take a group photo, the brightness in the picture is very average, I directly use the evaluation photometry.

I want to take an environmental portrait, the skin of the character is relatively white, and the surrounding environment is darker, so I choose local photometry to ensure that the exposure of the character is normal.

However, I do not want the brightness of the environment to be too outrageous, so I can choose the central focus on average photometry and take care of the environment.

When shooting the sunset, the brightness of the sun is very high and the brightness of the environment is very low. if I use evaluation photometry, the camera thinks that most of the picture is dark, so it will brighten the exposure, and the sunset I most want to shoot is overexposed. I certainly can't use the evaluation photometry mode. If I switch to a point metering mode and measure only a little bit of the sun, the camera can take a picture with normal exposure.

(3) although there are four photometric modes to make good use of exposure compensation, when I take pictures outside, I will encounter a variety of light environments. It is too troublesome to adjust the photometry mode every time. I usually only use evaluation photometry. If the exposure parameters obtained from the evaluation photometry are not accurate, I will use exposure compensation to increase or decrease exposure until the exposure is accurate.

Sometimes the sun is very strong outside and the camera screen is too dark, so it is easy to misjudge when checking whether the exposure is accurate.

At this point, you can open the "histogram" of the camera and know the exposure through the histogram.

(4) Photometry is not necessarily accurate. the standard of camera photometry is "18 gray", and the exposure parameter (F / S / ISO) generated by the camera also wants the brightness of the subject to be close to 18 gray. 18 gray is really easy to use, and the brightness of most objects is close to it, so the exposure is accurate.

But there is an exception to everything, and there are times when cameras go wrong.

For example, a pure white object, which is already white, is mistakenly thought by the camera to be so white and so bright, brighter than 18 gray. Look, I'll reduce the brightness a little bit for you.

Another example is a black object, which is already black, but the camera photometry mistakenly thinks that this thing is so black and so dark, darker than 18 gray. Look, I'll give you a little lower brightness.

The exposure of the photos taken at this time is not very accurate, so it is necessary to appropriately increase the exposure compensation for white objects and reduce the exposure compensation for black shooting, which is often called "white plus black subtraction".

This article is from the official account of Wechat: photography Research Society (ID:shoujiPhotography), by Zhang Xiaozhang.

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