What does the focal length of the camera mean?

The focal length is formed by the optical lens of the camera lens. A group of lenses with curvature (convex or concave) on both sides or one side are installed in the metal tube of a camera or projector to form a comprehensive lens.

The light emitted from different parts of the object, after passing through the lens, is focused on a point on the negative, so that the image has a clear outline and real texture. This point is called the focus. The focal length is the distance from the point in the lens of the lens to the point where the light can be clearly focused.

Extended data

Focal length f

According to the length of its focal length, that is, the viewing angle when shooting, the lens can be divided into standard lens, wide-angle lens and long focal length lens.

Standard lens, a general term for lenses with a viewing angle of about 50 degrees, and a photographic lens with a focal length approximately equal to the diagonal length of the photographed picture. Its viewing angle is generally 45 ~ 50. The lens with a focal length of 40-60 mm is 35 mm, the lens with a focal length of 6*6 cm is 75-80 mm, and the lens with a focal length of 4*5 inches is120-150 mm. ..

Wide-angle lens is a photographic lens with shorter focal length, larger viewing angle, longer focal length and smaller viewing angle than standard lens. Wide-angle lenses are divided into ordinary wide-angle lenses and ultra-wide-angle lenses.

A long focal length lens refers to a photographic lens whose focal length is longer than that of a standard lens. Telefocal lenses are divided into ordinary telephoto lenses and ultra-telephoto lenses. The focal length of ordinary telephoto lens is close to that of standard lens, while the focal length of ultra telephoto lens is much larger than that of standard lens.

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