Sloan Digital Sky Survey (SDSS) is one of the most common and important photometric systems in modern astronomy.
The large volume of survey data gotten by the SDSS team became the cultural legacy. Broad bandpass filters installed in the wide field cameras are defined on the basis of SDSS photometric system.
Asahi provided the world's first SDSS u, g, r, i, z-band filters to the 2.5 m telescope at Apache Point Observatory (APO) in New Mexico twenty years ago.
Unlike SDSS filters sold on internet, we produce under the spectral response in the 2.5 m telescope as SDSS project suggested.