[Lens] camera aperture

From: Http://tieba.baidu.com/club/8114767/p/511896 Aperture-the aperture that can be changed in diameter. It consists of several metal slices and is located between multiple lenses of the lens.
The aperture size is represented by the aperture coefficient, and is counted as F.
F = f (lens focal length)/d (aperture diameter)
When the lens focal length is fixed, the aperture coefficient is inversely proportional to the aperture diameter (valid. The aperture is divided into many files. The principle of the split is that the large aperture must be twice the light usage of the adjacent small aperture, that is, twice the light access area.
,... As F4, f5.6, F8, F11, F16...
F5.6 has two times of F11, and f5.6 has 1/2 of F4. The aperture is adjustable at or between two normal positions.
The aperture is used to adjust the incoming light volume and affect the depth of field and image definition.

Adjust the incoming light volume
The aperture is a light-through hole. When the aperture is large, more light is input, and the illuminance obtained from the sensor film is large, the aperture and shutter jointly control the exposure.

Depth of field affected

The depth of field refers to the depth range of a scene that can form a basic clear image on the photosensitive film. The larger the range is, the larger the depth of field is.
Front field: the point closest to the camera that can form a basic clear image.
Rear border of depth of field: the farthest point from the camera that can form a basic clear image.
From the front of the depth of field to the focus distance is called foreground depth, from the focus distance to the rear of the depth of field is called the rear depth of field. From the front of the depth of field to the rear of the depth of field, it is short for depth of field. The foreground depth is smaller than the rear depth of field.
The aperture size can change the depth of field.
Read depth of field from the camera: first look at the circle value used, for example, the F16 scale on both sides of the baseline for the distance ruler reading, that is, the front and back of the depth of field. For example, the distance between two scales of 16 on the depth of field scale is 2 meters before the depth of field, and 10 meters after the depth of field? #65310; segment? 0-2 = 8 meters (focusing at 3mm points)
Focusing on 3 M, aperture F8 is used, depth of field is 2.4 m, and depth of field is 4-2.4 = 1.6m. The depth of field range is reduced. The F16 to F8 aperture is increased by 2, and the depth of field is reduced by 6. 4 m.
It can be seen that the aperture affects the basic law of depth: aperture increases, depth of field decreases, aperture decreases, and depth of field increases.

Affects image definition

There are two reasons for the impact of clear image reading. One is the ball difference and the difference in wisdom produced by the lens itself (the distortion of the image can be understood by those who lack optical knowledge ), the larger the aperture, the smaller the aperture, and the smaller the aberration. The other is the diffraction phenomenon produced by the fluctuation of light. The smaller the aperture, the more serious the harm is. As a result, the camera has an optimal aperture, which is the best image quality. If the image quality is lower than the aperture, the diffraction phenomenon is enhanced and the image quality is also decreased. The optimal aperture of each camera is different. Generally, the maximum aperture is reduced to three places. When the lens quality is high, the first gear is reduced, and the quality is reduced to 4 ~ Grade 5. 

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