DX Encoding – What it is and how it became a standard for the analogue age
Dec 10, 2018
John Aldred
John Aldred is a photographer with over 25 years of experience in the portrait and commercial worlds. He is based in Scotland and has been an early adopter – and occasional beta tester – of almost every digital imaging technology in that time. As well as his creative visual work, John uses 3D printing, electronics and programming to create his own photography and filmmaking tools and consults for a number of brands across the industry.
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Have you ever wondered how some film cameras just know what speed ISO (or ASA) film you’re loading into it? Well, have you ever noticed those black and silver squares on the side of the roll? That’s called DX Encoding and that’s how the camera knows what film you’re using.
This video from photographer Azriel Knight goes deep into the origins of DX Encoding. He talks about how it was created, how it works, and how it was received when it was first introduced. And, no, it’s nothing to do with Nikon’s 1.5x crop cameras.
The system was developed by Kodak in January 1983. Popular Photography magazine at the time said “Kodak is making the DX system available free to all in the hopes it will establish itself as a universal system”. It was initially adopted to help the processing labs, rather than the photographers. It allowed their automated sorting and processing machines to more easily determine how to treat the film. The first cameras to utilise DX coding came in 1984.
The DX Camera Auto Sensing (CAS) system is made up of a set of conductive squares that the camera reads in order to figure out what ISO/ASA speed the film was, how many exposures are on the roll and how much exposure latitude it offers (how much you can under or overexpose it).
It still lives on today. All brands of 35mm film that we see available now from Kodak, Ilford, and many others still use DX encoding. However, it has not been completely without controversy over the years.
DX coding is something that many film photographers will already be familiar with. But if you’ve always wondered what those funny black & chrome squares are on your rolls of film, now you know.
John Aldred
John Aldred is a photographer with over 25 years of experience in the portrait and commercial worlds. He is based in Scotland and has been an early adopter – and occasional beta tester – of almost every digital imaging technology in that time. As well as his creative visual work, John uses 3D printing, electronics and programming to create his own photography and filmmaking tools and consults for a number of brands across the industry.
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One response to “DX Encoding – What it is and how it became a standard for the analogue age”
No IBIS that is the main reason why I didn’t buy one. I am going to keep using my a7rii until they do put it in their next camera .I’m getting tired of canon putting in incremental updates in their cameras why aren’t you like Sony and do it all at once like the a7iii what a perfect camera . Come on Canon stop ripping off your users.