DX I2/5 barcode on a 135-film cartridge

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.

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 film canister barcode

Codes on Kodak ISO 400 color negative film

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 six-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 four 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).

DX film edge barcode

Most film produced since 1983 contains a bar code at the bottom edge, which contains both the above "DX Number Part 1" and "DX Number Part 2".[1] This information identifies manufacturers and chemistry associated with their various film types. These codes are printed on the "data track" below another bar code called a "clock track". The data track also includes a start entry pattern, frame number information, including indicating if a position is a "half-frame", a parity bit, and an exit pattern. If the manufacturer and type of film negative is unknown, a negatives' edge bar code can be examined to identify this information.

Unlike the film canister DX number bar code, each frame or half-frame's data track code doesn't provide information about the total number of frames available in the roll.

See also

References

  1. ↑ DX CODES FOR 135-SIZE FILM. White Plains, NY: International Imaging Industry Association, Inc. (I3A). 2008.

Further reading

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