LENS

Camera Lens can be divided into three broad groups: wide-angle, standard, and long-focus. Extreme wide-angle lenses of focal length 6-8 mm, known as fish-eyes, give a very distorted image, with vertical and horizontal lines bowed. A standard lens of 50 mm often has a wide maximum aperture. Its angle of view is similar to that of the human eye. Long-focus lenses of 80-1200 mm are useful for large images of distant subject or when it is not possible to move close enough to use a shorter lens. The illustration and sequence of photographs bellow, which are all taken from the same viewpoint, show that, as the focal length of a lens increases, so the angle of a view decreases.