What does F2.8 on the camera mean?

F2.8 on the lens means that the aperture size of the lens is 2.8.

Aperture f value = lens focal length/lens effective aperture diameter. To achieve the same f value, the aperture of a long focal length lens is larger than that of a short focal length lens.

The size of the aperture will affect the amount of light entering and the depth of field. The smaller the f value of the aperture, the larger the aperture. Under the same ISO and shutter conditions, the larger the aperture, the brighter the picture will be. The relationship between aperture and depth of field: F2.8 large aperture is easy to cause shallow depth of field with blurred background; With the small aperture of F 16, the subject and background will be clearer.

The complete series of aperture values are as follows: f/ 1.0, f/ 1.4, f/2.0, f/2.8, f/4.0, f/5.6, f/8.0, f/1/kloc-0.

Extended data

The smaller the aperture f is, the larger the aperture is, and the more light enters per unit time, and the light entering at the upper level is exactly twice that of the lower level. For example, if the aperture is adjusted from F8 to F5.6, the amount of light entering will be doubled and the aperture will be enlarged by one level. The luminous flux of F5.6 is twice that of F8. Similarly, F2 is 16 times the luminous flux of F8. When F8 is adjusted to F2, the aperture is enlarged by four levels.

The function of the aperture is to determine the amount of light entering the lens. The smaller the value after f, the larger the aperture and the more light entering. On the contrary, the smaller. Under the condition that the shutter speed (exposure speed) is constant, the smaller the aperture f value is, the larger the aperture is, and the more light enters, the brighter the picture is; The larger the aperture f value, the smaller the aperture and the darker the picture.

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