A normal lens, often referred to as a standard lens, has a focal length approximately equal to the diagonal of the film or sensor format. This results in an angle of view and perspective that closely resembles what the human eye naturally sees, making images appear realistic and undistorted.
Normal lenses are popular for everyday photography, including portraits, street, and general-purpose shooting. Because they produce natural-looking proportions without the exaggeration of wide-angle lenses or the compression of telephoto lenses, they are often recommended as a versatile and reliable choice for photographers of all levels.