Editing DX number (section)

==Encoding==
===DX film canister barcode===
[[File:Kodak 400 color film DX code.jpg|right|thumb|DX CAS and barcode (315223, corresponding to DX number 95-2) on this 24-exposure roll of Kodak High Definition ISO 400 [[color print film]]]]

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 [[American National Standards Institute|ANSI]]/[[National Association of Photographic Manufacturers|NAPM]] IT1.14:1994 standard. Some film-processing machines optically scan the barcode when the cartridge is inserted for developing.<ref>{{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}}</ref>

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'' = [[hash function|hashed]] DX number
* ''E'' = suffix identifying the number of exposures

For 135 film cartridges the DX number is [[hash function|hashed]] to produce the four-digit code ''HHHH''. To generate this code, the combination code (aka DX Number Part&nbsp;1) is multiplied by 16 and added to the specifier number (aka DX Number Part&nbsp;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:

<math>16 \times 115+4 = 1844</math>

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:

<math>\frac{1844}{16} = 115+\frac{4}{16}</math>

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&nbsp;+&nbsp;3.

===DX film edge barcode===
[[File:Kodak Telegraph negativ23a.jpg|thumb|right|Film edge barcodes, below bottom sprocket holes; exposed Kodak BW400CN ([[black-and-white]] [[Chromogenic photography|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.<ref name=I3A-2008/><ref name=US5448049A>{{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.}}</ref> 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:<ref name=US4965628>{{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}}</ref><ref name=ISO1007>{{cite standard |title=ISO 1007 {{!}} Photography — 135-size film and magazine — Specifications |date=2000 |publisher=International Organization for Standardization}}</ref>{{rp|§6}}
* A six-bit entry code<ref name=ISO1007/>{{rp|§6.1.1.1}}
* A seven-bit film product class identification array (DX Number Part 1)<ref name=ISO1007/>{{rp|§6.1.1.2}}
* One unassigned bit, left blank<ref name=ISO1007/>{{rp|§6.1.1.3}}
* A four-bit film specifier array (DX Number Part 2)<ref name=ISO1007/>{{rp|§6.1.1.4}}
* A six-bit frame number<ref name=ISO1007/>{{rp|§6.1.1.5}}
* One bit to indicate if the position is a "half-frame"<ref name=ISO1007/>{{rp|§6.1.1.5}}
* A second unassigned bit, left blank<ref name=ISO1007/>{{rp|§6.1.1.6}}
* A parity bit<ref name=ISO1007/>{{rp|§6.1.1.7}}
* A four-bit exit code<ref name=ISO1007/>{{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.<ref name=US4965628/>

{|class="wikitable" style="font-size:90%;text-align:center;"
|+Sample data track code
! colspan=5 style="text-align:right;" | Position:
|  1 ||  2 ||  3 ||  4 ||  5 ||  6 ||  7 ||  8 || {{N/A}} ||  9
| 10 || 11 || 12 || 13 || 14 || 15 || 16 || 17 || 18 || 19
| colspan=6 {{N/A}}
|-style="font-size:150%;"
| style="background:#000;color:#fff;" | 1
| style="background:#fff;color:#000;" | 0
| style="background:#000;color:#fff;" | 1
| style="background:#fff;color:#000;" | 0
| style="background:#000;color:#fff;" | 1
| style="background:#fff;color:#000;" | 0

| style="background:#000;color:#fff;" | 1
| style="background:#fff;color:#000;" | 0
| style="background:#fff;color:#000;" | 0
| style="background:#000;color:#fff;" | 1
| style="background:#000;color:#fff;" | 1
| style="background:#000;color:#fff;" | 1
| style="background:#000;color:#fff;" | 1

| style="background:#fff;color:#000;" | 0

| style="background:#000;color:#fff;" | 1
| style="background:#000;color:#fff;" | 1
| style="background:#000;color:#fff;" | 1
| style="background:#000;color:#fff;" | 1

| style="background:#fff;color:#000;" | 0
| style="background:#000;color:#fff;" | 1
| style="background:#fff;color:#000;" | 0
| style="background:#000;color:#fff;" | 1
| style="background:#000;color:#fff;" | 1
| style="background:#000;color:#fff;" | 1

| style="background:#fff;color:#000;" | 0
| style="background:#fff;color:#000;" | 0

| style="background:#000;color:#fff;" | 1

| style="background:#fff;color:#000;" | 0
| style="background:#000;color:#fff;" | 1
| style="background:#fff;color:#000;" | 0
| style="background:#000;color:#fff;" | 1

|-
| colspan=6 | Entry code
| colspan=7 | Film product class<br/>(79 in this example)
| colspan=1 {{N/A}}
| colspan=4 | Film specifier<br/>(e.g., 15)
| colspan=6 | Frame no.<br/>(e.g., 23)
| colspan=1 | Half-<br/>frame
| colspan=1 {{N/A}}
| colspan=1 | Parity
| colspan=4 | Exit code
|}

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.