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
Sternal angle Sternal angle The sternal angle (also known as the angle of Louis or manubriosternal junction) is the synarthrotic joint formed by the articulation of the manubrium and the body of the sternum. The sternal angle is a palpable clinical landmark in surface anatomy. The sternal angle, which varies around 162 degrees in males, marks the approximate level of the 2nd pair of costal cartilages, which attach to the second ribs, and the level of the intervertebral disc between T4 and T5. In clinical applications, the sternal angle can be palpated at the T4 vertebral level. The sternal angle is used