The GOST 8874-1980 standard specifies methods for the determination of paper transparency and opacity, applicable to various types of paper. The standard details the equipment and instruments required for testing, including a reflectance photometer and a standard black cylinder, and specifies the preparation and testing procedures for the sample. By measuring the reflection factor of paper under specific lighting conditions, the standard enables the assessment of the Optical inspection properties of paper, helping to determine its suitability for practical applications. The determination of transparency and opacity is essential for quality control and performance evaluation of paper, ensuring the reliability and conformity of paper in areas such as printing, Encasement, etc.