A ring, located on the outside of the lens usually behind the focusing ring, which is linked mechanically to the diaphragm to control the size of the aperture; it is engraved with a set of numbers called f-numbers or f- stops. Artificial light:

Failing in the ability of a lens to produce a true image. There are many forms of aberration and the lens designer can often correct some only by allowing others to remain. Generally, the more expensive the lens, the less its aberrations (More attention to optical quality). While no single lens is called a 'perfect lens'. The "id [..]

This optical defect causes points on an object plane perpendicular to the lens axis to focus on a curved surface rather than a plane. c) Astigmatism

This optical defect causes the image of an off-axis point of light to appear as a comet-shaped blur of light. Coma, as well as curvature of field and astigmatism, degenerate the image forming ability of the lens at the rims of the picture. e) Distortion

A standard developed by Kodak and four other System Developing Companies - Canon, Fuji, Minolta and Nikon - based on a new film format and innovativefilm, camera and photofinishing technologies. Generally, APS cameras are more compact in size and weight. There are options in various sizes of print out and it will even provide a thumbnail prints (Co [..]

The area of a scene that a lens covers or sees. Angle of view is determined by the focal length of the lens. A wide-angle lens (short-focal-length) includes more of the scene-a wider angle of view-than a normal (normal-focal-length) or telephoto (long-focal-length) lens. It can also be explained as the extent of the view taken in by a lens. It vari [..]

Lens opening. The hole or opening formed by the metal leaf diaphragm inside the lens or the opening in a camera lens through which light passes to expose the film. The size of aperture is either fixed or adjustable. Aperture size is usually calibrated in f- numbers-the larger the number, the smaller the lens opening. Aperture affects depth of field [..]

A lens whose curved surface does not conform to the shape of a sphere; lenses are usually ground or moulded with spherical surfaces; because a spherical surface lens has difficulty in correcting distortion in ultra-wide-angle lenses or coma in large-aperture lenses brought about by spherical aberration, an aspherical lens is used. ASA:

The ratio of width to height in photographic prints - a traditional 35mm film frame is approximately 36mm wide and 24mm HIGH. This has an aspect ratio of 36:24, which can equally well be expressed as 3:2. Some digital cameras use the same aspect ratio for their digital images. For example most digital SLR (single lens reflex) cameras have a 3:2 asp [..]

System by which the camera lens automatically focuses the image of aselected part of the picture subject. AF-I & AF-S lenses: