 | This article needs additional citations for verification. (February 2022) |
The DX number was assigned by the International Imaging Industry Association (I3A). It uniquely identifies the type and manufacturer (sensitizer) of a film emulsion. A proprietary list of DX numbers for APS and 135 film was prepared yearly or as needed. (DX Codes for 135-Size Film, 2004, I3A; last edition was from January 2009). The list was available for sale from the I3A.