One of my favourite channels to watch on YouTube is Technology Connections. In each video, our host takes us on a journey through the histories of different technologies, explaining where they came from and how they work. It covers all kinds of technologies, but occasionally, the topic becomes somewhat related to photography or video. We’ve featured the channel here on DIYP before, to explain why cameras and our eyes see in RGB.
Now, he’s back to explain film. But it’s not a complete overview of how film is made, how it captures an image, how you can develop it or turn it into a print. Oh no, this super geeky video goes in-depth into one very specific aspect of 35mm film and that’s DX encoding – Or Digital IndeX). What is it? Why does it even exist? What does it do? And does it really matter?
At its simplest, it’s an early form of automated communication between the film roll and your camera, introduced by Kodak in 1983. It’s an “auto ISO” of sorts. It doesn’t automatically adjust your ISO to that of the scene before you – the way auto ISO mode works today. Instead, it allows your camera to know the speed of the film that’s loaded into it so it can adjust its meter accordingly. If you put Ilford FP4+ in there, the camera just knows to set the ISO to 125. Put some HP5+ or PANF in there, it knows to go to ISO 400 or 50 respectively.
It doesn’t seem like a geeky or complex enough topic to justify a 17-minute video, but when you watch the whole thing, you’ll realise just how wrong you are! Simply telling the camera the ISO rating of the film contained within is not the only information it stores!