Angle of view camera–subject distance to preserve the size of a subject, changing the angle of view can indirectly distort perspective, changing the apparent relative size of the subject and foreground. If the subject image size remains the same, then at any given aperture all lenses, wide angle and long lenses, will give the same depth of field. An example of how lens choice affects angle of view. This table shows the diagonal, horizontal, and vertical angles of view, in degrees, for lenses producing rectilinear images, when used with 36 mm × 24 mm format (that is, 135 film or full-frame 35mm digital
Angle of thumb approximations only. The angle between a line and a curve (mixed angle) or between two intersecting curves (curvilinear angle) is defined to be the angle between the tangents at the point of intersection. Various names (now rarely, if ever, used) have been given to particular cases:—"amphicyrtic" (Gr. , on both sides, κυρτός, convex) or "cissoidal" (Gr. κισσός, ivy), biconvex; "xystroidal" or "sistroidal" (Gr. ξυστρίς, a tool for scraping), concavo-convex; "amphicoelic" (Gr. κοίλη, a hollow) or "angulus lunularis", biconcave. The ancient Greek mathematicians knew how to bisect an angle (divide it into two angles of equal measure) using only