Projector Brightness - ISO 21118 standards

ISO (International Organization for Standardization) and IEC are both international organizations, and there is a cooperative relationship between the two, so the standards they set also have the nature of mutual reference. On August 26, 2005, three years after IEC released 61947-1, ISO and IEC jointly released the ISO/IEC 21118:2005 standard, which has only 15 pages, which is half of the 30 pages of IEC at that time. Of course, the main reason is that the other standards cited in it are not described in detail, but only the numbers are written. Subsequently, ISO21118 became the standard used worldwide after ANSI IT7.227 (Japan passed the domestic implementation of ISO standards the following year, so Japanese products will be marked with ISO lumens). After several iterations and updates, as of the time of writing this article (December 31, 2021), the latest version of the standard is the 2020 version released on February 1, 2020, namely ISO/IEC 21118:2020 (paid, 118 Swiss francs).
ISO21118 mainly includes five major tests, namely light source, audio output, background noise, maximum power consumption, and standard power consumption. The light source part contains several small items, such as "brightness", contrast, and uniformity. The test of the "brightness" part still continues to use the test method in IEC 61947-1, and the pre-adjustment chart also uses the 8-grid chart, but only some adjustments are made to the individual test environment. For example, in the 1990s, a three-gun CRT projector at a distance of 2.4 meters could only project a 60-inch screen, and the projection ratio was only 2.4m/0.74m=3.24. Today, it is unimaginable that the projection ratio of household telephoto projectors is generally 1.1-1.7. Therefore, the ISO standard sets adjustable ranges for the size and area of ​​the screen and the distance according to the projection ratio, but the overall test method itself has not changed, and it is still the 9-point illumination average method of ANSI, so the ISO lumen test results will not have a large difference from ANSI in terms of values.