How to hack the DX code

The DX code was introduced by Kodak in 1983 and is present on (almost) all the rolls of 35mm film.

There are three DX codes: two printed on the outside of the cartridge, and a pre-impressed one on the film edge. The one that interests us is the Camera Auto Sensing DX which allows the camera to learn about ISO, number of exposures and exposure tolerance. It is printed outside the roll and is composed by two rows of six rectangles each.


This code is composed of a “grid” of conductive areas (silver) and non-conductive ones (black):DXhackTAB to hack it you need to scrape off the insulating material or to isolate the sensitive parts. Here on the right there’s a scheme with the most used ISO values and their configuration in the matrix. (On Wikipedia you can find diagrams with all values).

While doing this you must consider the camera’s native settings because, especially for many point & shoot from the 80s, often is not supported an ISO value bigger than 400/1600! The risk is to have a reading of 100 ISO (the value at which these cameras automatically set themselves when there is an unknown/unreadable DX)

DXHack_17
DX code hacked to change the reading from 400 to 1600 ISO

Why do this? because in this way we can, for example, read a 400 ISO film as if it is 3200, and then use our favorite film for shooting in very low light situations (indoor/concerts), or we can pull our 100 ISO film up to 400 to achieve faster shutter speeds. Let’s say that the most used hack is towards 1600/3200 ISO because of the almost total lack of rolls with these sensitivities.

Once exposed a hacked roll of film, the new ISO value shall be given to the development laboratory so that they can use the correct development time.

6 thoughts on “How to hack the DX code

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