DX number

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.

This article is about film emulsion identifiers. For Document Exchange mail, courier and logistics in the United Kingdom, see DX Group.

DX I2/5 barcode on a 135-film cartridge

DX number composition

A DX number has two parts separated by a dash: the "combination code" also known as "DX Number Part 1" followed by a "specifier number", or "DX Number Part 2". For example, Agfa Perutz 3-color ISO 200/24° film is assigned 115-4 (I3A).

DX barcode

For 135-film cartridges the DX number is hashed to produce a four digit code. A suffix digit for the number of exposures and a manufacturer's proprietary prefix digit are concatenated to form a 6-digit decimal code. The code is printed in human-readable text and also represented as an Interleaved 2 of 5 barcode. Size and position conform to the ANSI/NAPM IT1.14:1994 standard.

To generate digits 2 through 5, the combination code is multiplied by 16 and added to the specifier number. The result is prefixed with zeroes to make 4 digits. For the Agfa film 115-4 above, the digits would be 1844 (16 × 115 + 4).

Digit 1 is any digit from 0 to 9 and is assigned by the manufacturer.

Digit 6 is a code digit for the number of full-frame exposures: 1 is for 12 exposures, 2 for 20 exposures, 3 for 24, 4 for 36, 5 for 48, 6 for 60, 0 for 72 and 7 for non-standard lengths such as 24 + 3.

The barcode is located between the electrically-read silver and black DX Camera Auto-Sensing Code and the film cartridge exit lip.

The barcode is optically scanned by many film-processing machines when the cartridge is inserted for developing (Kodak patent 5761558).

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See also

Further reading
  • "Film Emulsion Codes" (PDF). 1.14. evertz. 2012-05-01. Archived (PDF) from the original on 2017-06-09. Retrieved 2019-06-09.
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