Traditional Culture Encyclopedia - Photography and portraiture - Working principle of aperture in photography
Working principle of aperture in photography
A photographic term, which is a device used to control the amount of light entering the photosensitive surface of the fuselage through the lens, is usually set in the lens. Usually we use the value of f to indicate the aperture size. Generally speaking, it is impossible to change the lens diameter at will when taking pictures.
However, the luminous flux can be controlled by adding a polygonal or circular variable aperture grating inside the lens. This device is called an aperture. Aperture is a camera lens composed of several extremely thin metal sheets, through which light can pass. The amount of light entering the lens is controlled by changing the size of the hole.
The larger the aperture, the more light enters the lens. Aperture values are usually expressed by f/ 1 and f/2. The larger the number, the smaller the aperture, and vice versa. Under the condition of constant shutter speed, a proper aperture size can bring normal exposure. Excessive aperture will lead to overexposure, while too small aperture will lead to underexposure.
Aperture is not only used to adjust the exposure, but also to control the depth of field of the picture. The relationship between depth of field and aperture is that the larger the aperture, the shallower the depth of field, and the smaller the aperture, the deeper the depth of field. The smaller the aperture, the greater the corresponding value of f, for example, the aperture of f/22 is smaller than that of f/ 16.
Shutter and depth of field are related. Because a large depth of field requires a small aperture, and in order to ensure proper exposure, the shutter speed will slow down accordingly. There are also two factors that restrict the depth of field: focal length and telephoto distance (object distance). For different cameras, the focal length is different.
The actual shooting distance is affected by the specific environment. Light is also an important constraint. Especially outdoor photography, it is difficult to meet the appropriate light intensity. Therefore, more practice is an effective way to master these skills. Perhaps, after you click, you will get more valuable harvest.
As we all know, the imaging principle of the camera is pinhole imaging. The focal length is a fraction of the diameter of the hole, which is the aperture size. Through the pinhole imaging experiment in physics class, we know that the smaller the pinhole, the clearer the imaging.
Therefore, when taking landscape photos, we set the aperture to 1 1 or 16, so that the near and far scenes are clear. When taking portraits, we put the aperture at 1.4 to make the figures clear and the background blurred.
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