DX encoding

As DX coding ( DX stands for English Digital indeX ) ANSI PH1.14 and I3A - standardized, coded, electrically readable markings are referred to cartridges of photographic film.

Operation

In the encoding, among others, information on the film speed, the exposure latitude and length of the movie are included. Some of the information used for camera control, another of the laboratory processing. Since it is automation functions, the photographer comes normally with DX coding not in contact.

The DX Code includes the following components:

  • Code chessboard (CAS) on the film cartridge;
  • Line and number code on the film cartridge;
  • Information field to the film cartridge;
  • Barcode on the edge of the film in color negative films.

The outer packaging DX - coded films usually shows a "DX" - or " DXN " icon to indicate the presence of a corresponding encoding.

Chessboard code

The CAS code called ( for Camera autosensing code) checkerboard DX coding on miniature films in the format 135 is the camera control; the information contained are automatically read out from the most automated cameras and taken into account in the exposure. Older or simple camera models however, only read the film speed.

The code consists of a total of 12 fields in two rows either conductive (silver or blank ( white here in the illustration); encodes a logical 1) or non-conductive ( black or lacquer; encodes a logical 0), so that the corresponding contacts are bridged on the camera or not; So the information is binary coded.

  • Field 1 and 7: Ground ( Common);
  • Box 2-6: Film sensitivity (film speed );
  • Field 8 to 10: Number of shots (exposure counts);
  • Section 11 and 12: exposure latitude (Exposure Tolerance).

The top row contains, from left to right the fields 1 to 6, the lower the fields 7 to 12, the cartridge is to be regarded as that of the film slot is facing up.

The DX - iX- coding at APS film ( film size IX240 aka Advantix ) is made considerably more fields and stores - according to APS specifications - additional information.

Film speed

The film speed is defined in the DX coding in 1/ 3 EV steps between ISO 25/15 ° to ISO 5000/38 °; in general, however, film speeds above ISO must be 1600/33 ° set manually on the camera. In addition to the 24 pre-defined values ​​are 8 additional values ​​for special settings are available ( one for each sensitivity group), but these are not, or interpreted by most cameras in different ways.

Especially simple cameras can contacts for the reading of the film speed also work with a reduced number. If, for example, the exposure latitude typical negative films exploited enough for a rough detection sensitivity in all stages have the contact fields from 1 to 4. If one limits the supported range, which contact fields 1-3 are only needed. If even only be distinguished between two allowed sensitivities, only two contacts are needed.

Running time

The film length or image number (record number ) is in the DX coding with 12, 20, 24, 36, 48, 60 and 72 shots coding ( "Non - Standard" is also available ) is defined and is encoded with three bits.

Exposure latitude

Exposure latitude is the DX coding with / - 1 defined aperture, 2 / -1 aperture and 3 / -1 Aperture - 1/ 2 stop, /.

Example

The film cartridge shown here has the following DX coding on ( the bar code is not taken into account ):

Fields 1, 3 and 6 ( starting from the top left in the figure) are conductive, the film speed is so ISO 125/22 °; Sections 7, 8 and 9 (starting in the figure below left) are conductive, so the film has 24 pictures; The last two fields are also conductive, so the film has a latitude of 3 / -1.

Barcode

The bar code contains processing information for reproducing equipment; it includes information on the manufacturing process, the film type, film speed and the film length.

Color negative films can also be provided with a bar code on the edge of the film, which contains a product identification; Also this information is only relevant for automated film processing in reproducing equipment.

History and Development

The developed method of Kodak DX coding for the 135 film format was introduced on 3 January 1983 ( Kodak Press Announcements 1-83-1425 and 1-83-1427 ) in order to simplify the handling of miniature films. In contrast to previous stand-alone solutions, such as the mechanism introduced by Fujifilm in the year 1977 135 - cartridge system with electrical contacts for detecting the film sensitivity, found Kodak's DX code broad market acceptance quickly.

The first film with DX code was introduced in March 1983 color negative film Kodacolor VR -1000. Today, most miniature films are DX -coded, only in products from Eastern Europe, Russia and Asia are missing these codes frequently.

As the first 35mm camera, which used the DX code, Konica TC -X SLR applies. Pentax takes for the Pentax Super Sport 35 (PC 35AF -M) from 1984 the title of the first non- SLR with DX support and for the A3 / A3000 from 1985 the title of the first SLR with DX code support to complete. The first Minolta cameras with DX - code support were presented in July 1984 compact camera AF - I / Freedom II and presented in February 1985 Minolta 7000 AF. For Nikon this feature was also introduced with the F- 301 / N2000 still 1985.

An extended version is DX - iX ( data exchange - information exchange ), which was introduced with the Advanced Photo System in 1996 and exclusively for APS - films ( film format IX240 aka Advantix ) will be used.

Since about 1998, the DX code similar identification system is also available for roll film formats 120 and 220 available, which was introduced by FujiFilm under the name barcode system. This film format and length, film speed and the film type is encoded in the context of a bar code on the label, which connects the light-sensitive film with the backing paper. This barcode can be read by a number of recent medium format cameras.

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