APS-H is a designation for the size of an image sensor used in some digital cameras. Its dimensions are approximately 28 × 19 mm, which places it between the smaller, more commonly used APS-C format and the larger, so-called "full-frame" sensor, which corresponds in size to a 35mm film frame. Compared to a full-frame sensor, APS-H is smaller and therefore captures only a certain crop from the image projected onto it by the lens. This phenomenon is called "crop factor" or focal length multiplier, and in the case of APS-H, its value is approximately 1.3×. In practice, this means that the lens used will have an angle of view corresponding to 1.3 times its focal length. For example, a 100mm lens on a camera with an APS-H sensor will behave like a 130mm lens on a full-frame body. This format was historically used primarily in professional DSLRs, where it offered a compromise between image quality and continuous shooting speed.
