What is the principle that the camera can adjust the far and near focal length?

The camera can adjust the far and near focal length by using the optical principle. The focal length is the distance from the main point to the focal point after lens optics. The length of focal length determines the imaging size, viewing angle, depth of field and perspective of the picture.

Focal length is the distance of parallel light from the optical center of the lens to the focusing point. It is also the distance from the center of the lens to the imaging plane such as the backplane or CCD in the camera. When the distance from the optical center to the focal point increases, the depth of field becomes larger, and when the distance from the optical center to the focal point decreases, the depth of field becomes smaller.

Extended data

The lens of a camera is a set of lenses. When the light parallel to the main optical axis passes through the lens, it will converge to one point. When the light parallel to the main axis of the convex lens passes through the convex lens, it will converge to a point on the other side of the convex lens. The distance from the focal point to the optical center of the convex lens is called the focal length of the convex lens. There is a focal point on each side of the convex lens.

A special point on an optical center lens at which the propagation direction of light passing through it remains unchanged. The lens of the camera we use is equivalent to a convex lens, and the film (or the photosensitive device of a digital camera) is near the focal point of the convex lens, or the distance from the film to the optical center of the convex lens is about equal to the focal length of the convex lens.

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