Basic knowledge of camera lens

Lead: What does the focal length of the lens mean? What is a standard lens? What is a telephoto lens? What is a short-focus lens? What is a zoom lens? What are their uses, advantages and disadvantages?

The basic knowledge of camera lens focal length is an important parameter of optical lens. When a beam of parallel light passes through the convex lens along its main axis, it will converge to a point on the other side of the convex lens, which is called the focal point, and the distance from the focal point to the optical center of the convex lens is called the focal length of this convex lens. Photographic lenses, like convex lenses, have standard focal lengths, long focal lengths and short focal lengths.

Focal length = the diagonal length of the imaging frame is called standard lens 135. The diagonal of the camera frame is 58mm, the diagonal of camera 135 is 58mm, and the diagonal of camera 120 is 75 mm. What is longer than the standard lens is called a long focal length lens, and what is shorter than the standard lens is called a short focal length lens.

Lenses with different focal lengths have different modeling characteristics, for example, short focal length lenses have the characteristics of wide viewing angle, large depth of field, large perspective effect and small imaging. These characteristics are used in creation, that is, modeling means.

A lens with variable focal length is called a zoom lens, and the ratio of the shortest focal length to the longest focal length is called the zoom multiple of the zoom lens. Under the same shooting distance, the larger the zoom factor, the more significant the scene change.

From the focal length, the lens with wide angle and large zoom factor is the best, which is mainly used for professional photography, with high cost and the most expensive price.