Ultra Wide Angle - Fisheye Lenses
Fish eye lenses are basically ultra wide angle lenses and they are known as both. The focal lengths of fish eye lenses depend on the film format. They have a short focal length of less than about 17mm for a 35mm camera. Common fish eye focal-lengths for a 35 mm camera are 6mm - 8mm, which will give you a circular image, and 15mm or 16mm, which will give you a curvilinear, full-frame, image. The ultra wide angle view these lenses give you results in deliberate image distortion as straight lines may appear to be curved and curved lines may appear to be straight. Fish eye lenses make objects appear to quickly shrink in size as the distance from the camera increases and the objects close to the camera appear far apart. These lenses offer a good depth of field. Focusing may not always be necessary with a fisheye lens as the depth of field often extends from only inches in front of the lens to infinity. The angle of view with a fisheye lens usually exceeds 100 degrees and sometimes more than 180 degrees.
Fish eye lenses range in price from about $60 to several thousand. Lenses come in different apertures and in auto and manual focus models.