About standard lens, wide angle lens, telephoto lens.

Standard lens is also called standard focal length photographic lens. The standard lens has a viewing angle of about 50°, and the focal length is approximately equal to the diagonal length of the imaging carrier. The standard lens is designed based on the angle of view of the human eye (around 50°). Standard lenses can be divided into standard fixed focus lenses and standard zoom lenses. Because the primary basis for dividing the focal length is not the absolute value of the focal length, but the imaging angle of view as the standard. Therefore, depending on the size of the frame (film or sensor), the imaging angle of view must be different, and the focal length of the standard lens is of course also different.

The standard lens is the most widely used in general photography because of its angle of view, focal length, depth of field, image magnification, perspective ratio, etc., suitable for human visual habits, so it is called the primary lens. Compared with other lenses, the standard lens has the smallest aberration and relatively good image quality, so it has a wide range of applications and is especially suitable for shooting portraits. Therefore, in order to reduce distortion, a wide-angle lens or a telephoto lens is not necessary for shooting with a standard lens. Because the viewing angle and focal length of the standard lens are specific, regular use of the standard lens can exercise one's basic skills and improve the photographer's judgment ability and unconscious memory ability.

Wide-angle lens, also known as short-focus lens, has an angle of view greater than 60° and a focal length smaller than the diagonal length of the imaging carrier. Wide-angle lenses can be divided into wide-angle fixed-focus lenses and wide-angle zoom lenses. The wide-angle lens can shoot a wide range of scene space, with strong spatial visual effects, a large depth of field, and a strong sense of three-dimensionality. The expressive power of the close-up is strong, and the close-up seems to be enlarged, becoming sparse and scattered. The expressive power of the perspective is weak, the perspective seems to shrink, become denser and converge. When shooting with a wide-angle lens, especially close-up, the scene will lose its normal perspective relationship to varying degrees, and the image will be distorted to varying degrees.

Telephoto lens, also known as telephoto lens, narrow-angle lens. The viewing angle is smaller than that of the human eye (about 50°), and the focal length is longer than the diagonal length of the imaging carrier. The viewing angle is greater than 20°, and the focal length is 80-150mm, which is called ordinary telephoto lens; the viewing angle is 10°-20°, and the focal length is 150-300mm, which is called medium telephoto lens; the viewing angle is less than 10° and the focal length is above 300mm, commonly known as " "Cannon" is an ultra-telephoto lens. The telephoto lens has a small angle of view and can only shoot a narrow space range of the scene, with weak spatial effects, weak stereo perception, and small depth of field. The telephoto lens has a high magnification ratio, which can bring the distant scene closer, and has a strong expressive power for the distant scene. The distant scene seems to be enlarged, becoming sparse and scattered; the expressive power for the near scene is weak, and the near scene seems to be reduced, dense and converged. For the golden photo, the perspective distortion is small, which is conducive to the reproduction of the details and texture of the scene.