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
Octagon is then as above: Expressed in terms of the span, the area is Another simple formula for the area is More often the span "S" is known, and the length of the sides, "a", is to be determined, as when cutting a square piece of material into a regular octagon. From the above, The two end lengths "e" on each side (the leg lengths of the triangles (green in the image) truncated from the square), as well as being formula_12 may be calculated as The circumradius of the regular octagon in terms of the side length "a" is and the