This standard specifies two methods for determining the transmittance and haze of transparent plastics in the form of plates, sheets, and films. Method A is the haze meter method, while Method B is the spectrophotometer method. The core testing instrument corresponding to this standard is the transmittance and haze tester. Such instruments typically employ a specific optical structure with an integrating sphere for photoelectric reception, enabling automatic and rapid measurement of the ratio of total transmitted light to scattered light after light passes through the material, thereby calculating transmittance and haze values. The instruments are usually equipped with an open sample window and a microcomputer processing system, making them easy to operate and widely used for optical performance testing in industries such as plastics, films, and packaging.