dx codes on film canister

Deciphering Film Cassettes

Just what do those metal strips on your film cassetes do?

One interesting question that I get asked from time to time is how to manually encode DX information on film cassettes. I documented this in the original manuscript for my Nikon Field Guide, but unfortunately it was one of the things that had to be left out due to page count limitations. You can find a set of foils that can be used to change DX coding on Amazon here: (hint: search for “DX Coded Film Labels”),, but I have rarely seen the information you need to make your modifications documented.

DX coding is specified by an international standard: ANSI/NAPM Standard IT1.14:1994. Refer to the picture of the film cassette, above, for the 12 positions where conductive metal strips can be applied.

  • Positions 1 and 7 on the left are always set to conduct (i.e., are metallic areas). They are used for alignment purposes.
  • The ISO value of the film is indicated by positions 2-6 in the top row. Film speeds from ISO 25 to 5000 can be encoded.
  • The number of exposures are indicated by positions 8-10 in the bottom row. Note that many Nikon bodies can actually get an extra exposure off most film when loaded correctly.
  • Finally, the exposure latitude is indicated by positions 11-12 in the bottom row. Latitude is used by some automatic processors for print film, but is not relevant to slide film (note that the Kodak Gold film in the above photo shows that it has +3 to -1 stop latitude).

See the above picture for positions; see the tables below to decode. Remember, the conductive areas are reflective silver, the other areas are non-conductive and usually black (a few manufacturers use a different base color on some cassettes).

ISO Value Position 2 Position 3 Position 4 Position 5 Position 6
25 None None None Silver None
40 None None None Silver Silver
50 Silver None None Silver None
64 Silver None None None Silver
80 Silver None None Silver Silver
100 None Silver None Silver None
125 None Silver None None Silver
160 None Silver None Silver Silver
200 Silver Silver None Silver None
250 Silver Silver None None Silver
320 Silver Silver None Silver Silver
400 None None Silver Silver None
500 None None Silver None Silver
640 None None Silver Silver Silver
800 Silver None Silver Silver None
1000 Silver None Silver None Silver
1250 Silver None Silver Silver Silver
1600 None Silver Silver Silver None
2000 None Silver Silver None Silver
2500 None Silver Silver Silver Silver
3200 Silver Silver Silver Silver None
4000 Silver Silver Silver None Silver
5000 Silver Silver Silver Silver Silver
Exposure Count Position 8 Position 9 Position 10
12 exposures Silver None None
20 exposures None Silver None
24 exposures Silver Silver None
36 exposures None None Silver
72 exposures Silver Silver Silver
Exposure Latitude Position 11 Position 12
+/- half stop None None
+/- full stop Silver None
+2 to -1 stop None Silver
+3 to -1 stop Silver Silver

So for the film cassette shown at the top of the page:

  • 2,3,5 indicate ISO 200
  • 10 indicates 36 exposures
  • 11, 12 indicates +3 to -1 stop latitude