Perspective

Perspective is the visual effect of moving a subject which is in the foreground closer to or further from the background. If you take photographs with lenses of different focal length while keeping the size of the subject in the foreground constant, the background appears to be further away and the sense of perspective is exaggerated with a short focal length wide angle lens. With a long focal length telephoto lens, the background appears to be closer to the subject and the sense of perspective is lessened. You can greatly change the feeling of presence even with the same subject by using this sense of perspective.

Fisheye lens – extreme perspectives
AF10-17mm f/3.5-4.5 Fisheye Picture

Common wide-angle lenses for a full-frame 35 mm camera are 35, 28, 24, 21, 18 and 14 mm. Many of the lenses in this range will produce a more or less rectilinear image at the film plane (though some degree of barrel distortion is not uncommon here).

Extreme wide-angle lenses that do not produce a rectilinear image are called fisheye lenses. Common focal lengths for these in a 35 mm camera are 6 to 8 mm (which produce a circular image). Lenses with focal lengths of 14 to 16 mm may be either rectilinear or fisheye designs.

Wide-angle lenses come in both fixed-focal-length and zoom varieties. For 35 mm cameras, lenses producing rectilinear images can be found at focal lengths as short as 12 mm, including zoom lenses with ranges of 2:1 that also begin at 12 mm.