DX (Digital indeX) encoding is an ANSI and I3A standard, originally introduced by Kodak in March 1983, for marking 135 and APS photographic film and film cartridges. It consists of several parts, a latent image DX film edge barcode on the film below the sprocket holes, a code on the cartridge used by automatic cameras, and a barcode on the cartridge read by photo-finishing machines.
In order to simplify the handling of 35 mm film in 135 format Kodak introduced the DX encoding method on 3 January 1983.[1][2] In contrast to former solutions like Fuji's film speed encoding method in 1977,[3] which was already using electrical contacts for film speed detection on 135 format cartridges,[4] Kodak's later DX code system immediately met success in the marketplace.
The first cameras to use the technology was the Konica TC-X SLR (1985),[5] as well as the compact cameras Pentax Super Sport 35 / PC 35AF-M[6]and Minolta AF-E / Freedom II[7] in 1984. Pentax instead claimed the A3 / A3000 was the first DX-enabled SLR in 1985.[8] Other DX-enabled SLRs were introduced in 1985 as well: Minolta 7000[9] (February 1985) and 9000 (September 1985), as well as the Nikon F-301 / N2000.
DX-iX (data exchange - information exchange) is an expanded DX encoding system introduced in 1996 to be used in conjunction with the Advanced Photo System (APS). It is only used on APS films format IX240, also known as Advantix.
In 1998, Fujifilm introduced a film identification system for 120 and 220 format roll film called Barcode System (with logo "|||B"). The barcode encoding the film format and length as well as the film speed and type is located on the sticker between the emulsion carrying film and the backing paper.[10][11][12][13][14] This 13-bit barcode[10][11][12][13][14] is optically scanned by newer medium format cameras like the Fujifilm GA645i Professional, GA645Wi Professional, GA645Zi Professional, GX645AF Professional, GX680III Professional, GX680IIIS Professional, Hasselblad H1, H2, H2F and H3D Model I with HM 16-32 as well as by the Contax 645 AF.[10]
Next to the film exit lip is an Interleaved 2 of 5 barcode and a printed number. The six digits represent the I3A assigned DX number (middle four digits), the number of exposures (last digit) and a proprietary manufacturer's code (first digit). The DX number identifies the manufacturer, film type, and by inference, the necessary developing process type. This is used by automatic photo-finishing machines to correctly process the exposed film.[15]