Focal Length

Each lens has a focal length. Technically, when using a lens to project a focused image onto a surface, the focal length is the distance between the lens & the surface. In cameras, this distance would be the distance between the camera lens and the photographic film. However, it isn't really that simple. Camera lenses are actually more complex than simple lenses. When dealing with photography, 400mm lenses aren't necessarily 400mm long. So, in cameras, where the focus length doesn't technically measure the distance between the lens and the film, there is another important characteristic associated with the focal. As focal length varies, so does the angle of view that your lens captures. This is the important difference between photographic lenses of different focal lengths. The bigger the focal length, the smaller the angle of view. Basically, this means that as the focal length increases, so does the magnification of the image projected by the lens.

When dealing with 35mm photography, 50mm is the standard size lens. Smaller than 50mm, is considered a wide angle lens. Wide angle lens capture a wide angle of view. Focal lengths larger than 50mm, in the 80mm and up range, is considered to be a telephoto lens. These lenses capture a narrow angle of view, which translates into a magnified image.