Cracking the DX code is nothing as glamorous as cracking the DNA code. But it is something everyone can easily do. Most cameras come equipped with DX coding, and most can be disabled with a manual ISO setting override. But there are some compacts and SLRs which cannot be overridden. Or sometimes, the odd roll of film may not be DX coded. Other than screaming and pulling your hair out, is there anything you can do?
 

Of course you can do something about those arrogant computers. Show them who's boss! Let them know you decide the film speed, not them. DX coding is a system of film coding that is almost universally adopted by film manufacturers to denote the characteristics of the film onto the 35mm film canister in a format that can be read by a camera's DX contacts. DX coding consists of a series of black or silver squares on the side of the canister. Silver is an unpainted square and allows electricity to flow between the two contacts on the silver square. Black is painted and thus non-conductive. Through the series of contacts, the camera reads the pattern of squares and decodes the type of film in the canister.
 

What are the information encoded in the DX code? Exposure latitude, length of film and ISO speed are all encoded on the squares. By changing the pattern of the squares, you can fool the cameras about what film type is in the camera. You can scrape off black paint to make a black square silver, or paste stickers over silver squares to make it appear "black" to the DX code contacts.
 

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