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
Type 90 AFV rear; the latter open outwards. In each side of the hull there are three firing ports with periscopes. On either side of the forward hull, a cluster of four 76 mm smoke grenade dischargers is mounted. The vehicle is fully amphibious, a folding trim board stowed at the front of the hull needs to be raised, and the vehicle can then propel itself in the water using its tracks. Standard equipment includes an NBC system, a Type 889 radio, and a Type 803 intercom system. Type 90 AFV The Type 90 is an armoured fighting vehicle produced by Chinese company