DX number

A DX number has two parts separated by a dash: CCC-SS

1. CCC is the "combination code", also known as "DX Number Part 1", which identifies the manufacturer and emulsion type
2. SS is the "specifier number", or "DX Number Part 2", which distinguishes between different varieties within the same family of emulsions

For example, Agfa Perutz 3-color ISO 200/24° film is assigned 115-4, while the equivalent Perutz 3-color ISO 100/21° film is assigned 115-3.{{cite web |url=https://www.yumpu.com/it/document/view/3454560/dx-codes-for-135-size-film-international-imaging-industry-association |title=DX Codes for 135-Size Film |date=February 2008 |publisher=International Imaging Industry Association, Inc. (I3A) |location=White Plains, NY |access-date=22 October 2024}}{{rp|12}}

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DX Part 1 numbers, from the 2008 DX Codes document:

File:Kodak 400 color film DX code.jpg]]

The DX film canister barcode is printed in human-readable text and also represented as an Interleaved 2 of 5 barcode, located between the electrically read silver and black DX Camera Auto-Sensing Code and the film cartridge exit lip. The size and position conform to the ANSI/NAPM IT1.14:1994 standard. Some film-processing machines optically scan the barcode when the cartridge is inserted for developing.{{cite patent |country=US |status=Patent |number=5661558A |invent1=David Lynn Patton |invent2=Lawrence Joseph Travis |invent3=Douglas Andrew McPherson |pridate=June 5, 1995 |pubdate=June 2, 1998 |assign=Eastman Kodak Co |title=Expanded film cartridge bar code}}

This film canister barcode is a six-digit number in the format PHHHHE, where:

• P = proprietary prefix ranging from 0 to 9, assigned by the manufacturer
• HHHH = hashed DX number
• E = suffix identifying the number of exposures

For 135 film cartridges the DX number is hashed to produce the four-digit code HHHH. To generate this code, the combination code (aka DX Number Part 1) is multiplied by 16 and added to the specifier number (aka DX Number Part 2). The result is prefixed with zeroes, if necessary, to make four digits. For the Agfa film assigned DX number 115-4 above, the hashed 4-digit code would be 1844:

$16\; \backslash times\; 115+4\; =\; 1844$

The DX number can be recovered from the hashed code by dividing by 16, which gives the Part 1 number as the largest whole integer and the Part 2 number as the remainder:

$\backslash frac\{1844\}\{16\}\; =\; 115+\backslash frac\{4\}\{16\}$

The suffix digit E 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.

File:Kodak Telegraph negativ23a.jpg chromogenic) film, DX number 79-15]]

Most film produced since 1983 contains barcodes along the bottom edge of the film, recorded in two parallel tracks. The upper track (closer to the sprocket holes) is called the "clock track" and the lower track (along the edge of the film) is called the "data track"; the data track contains the unhashed DX number.{{cite patent |country=US |status=Patent |number=5448049A |title=Film latent image bar-code (LIBC) reader |invent1=Mark E. Shafer |invent2=Robert W. Easterly |pridate=February 16, 1994 |pubdate=September 5, 1995 |assign=Eastman Kodak Co.}} However, unlike the film canister DX number bar code, each frame or half-frame's data track code does not provide information about the total number of frames available in the roll.

The data track consists of:{{cite patent|country=US|number=4965628A|title=Photographic film with latent image multi-field bar code and eye-readable symbols|status=Patent|pubdate=1990-10-23|gdate=1990-10-23|inventor1-last=Olliver|inventor2-last=Johnson|inventor3-last=Patton|inventor1-first=Richard|inventor2-first=Cortlandt|inventor3-first=David |assign=Eastman Kodak Company}}{{cite standard |title=ISO 1007 {{!}} Photography — 135-size film and magazine — Specifications |date=2000 |publisher=International Organization for Standardization}}{{rp|§6}}

• A six-bit entry code{{rp|§6.1.1.1}}
• A seven-bit film product class identification array (DX Number Part 1){{rp|§6.1.1.2}}
• One unassigned bit, left blank{{rp|§6.1.1.3}}
• A four-bit film specifier array (DX Number Part 2){{rp|§6.1.1.4}}
• A six-bit frame number{{rp|§6.1.1.5}}
• One bit to indicate if the position is a "half-frame"{{rp|§6.1.1.5}}
• A second unassigned bit, left blank{{rp|§6.1.1.6}}
• A parity bit{{rp|§6.1.1.7}}
• A four-bit exit code{{rp|§6.1.1.8}}

This information identifies manufacturers and chemistry associated with their various film types. If the manufacturer and type of film negative is unknown, the data track can be examined to identify this information. The frame number and half-frame indicator are extensions to the original data track, added by Kodak in 1990.

For each of the three encoded numerals, the most significant digit is on the left and the least significant digit is on the right; for example, the film class is a seven-bit number encoded in positions 2 through 8; position 8 is the least significant digit, and position 2 is the most significant digit. In this example, the binary number encoded (1001111) for the film class is equal to 79 (base-10). The parity bit is set or left blank to ensure the total number of "1" bits in positions 1 through 12 plus the parity bit is even. In this example, there are nine "1" bits in positions 1 through 12, so the parity bit is set.

• DX encoding

• {{cite web |title=Film Emulsion Codes |date=2012-05-01 |version=1.14 |publisher=evertz |url=https://evertz.com/resources/FilmID.pdf |access-date=2019-06-09 |url-status=live |archive-url=https://web.archive.org/web/20170609043649/http://www.evertz.com/resources/FilmID.pdf |archive-date=2017-06-09}}

• [https://industrieplus.net/dxdatabase/index.php A database of DX numbers]

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Category:Photographic film markings