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
Hyperbolic angle identities use the number "i" to remove the alternating factor (−1) from terms of the series to restore the full halves of the exponential series. Nevertheless, in the theory of holomorphic functions, the hyperbolic sine and cosine functions are incorporated into the complex sine and cosine functions. Hyperbolic angle In mathematics, a hyperbolic angle is a geometric figure that defines a section of a hyperbola. The relationship of a hyperbolic angle to a hyperbola parallels the relationship of an "ordinary" angle to a circle. Hyperbolic angle is defined in terms of the "standard" rectangular hyperbola: "y" = 1/"x", for positive