Ultra wide angle lens the difference is only whether distortion is present or not. However, the shorter the focal length, the more difficult it is to implement rectilinear correction. In fisheye lenses, the visual angle is close to or more than 180 degrees in at least one direction. For example, a "diagonal fish eye" would have a viewing angle of at least 180 degrees within the diagonals of the frame. A "circular fisheye" would represent the image in the form of a circle. Rectilinear ultra-wide angle lenses are used in photography and cinematography sometimes to achieve three-dimensional perspective distortion instead of simply two-dimensional barrel
Nambu Type 90 than the Imperial Army's Type 10 for a few good reasons. First, they were made in lower numbers than the Army type. Second, they were usually issued to ships and Naval aircraft and were lost when they were destroyed or sank. Third, Soldiers and Marines who found flare guns on the battlefield often threw them away, as they were not seen as collectable as pistols, rifles, or knives. In Hollywood movies (like "Demolition Man (1993)" and "Waterworld (1995)"), the Type 90 is used erroneously as a stand-in for a futuristic shotgun pistol. Nambu Type 90 The Nambu Type 90 was