What is DX film encoding and how do cameras use it?
Asked 1/12/2019
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I’m asking about DX encoding on 135/35mm film cartridges. What information does it provide, how do cameras read it, and when did it become common? Also, how can I tell whether my film camera supports DX reading, and what happens if I use DX-coded film in a camera without DX support or non-DX film in a camera that does support it?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
7y ago
2 Answers
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That DX is a barcode system stating ISO, printed on the film canister, so the camera and photo finisher can identify it. The canister has a conductive/nonconductive code that electrical sensors in camera can read.
Wikipedia says it started in 1983 and has details. See your camera manual, but if the camera offers it, DX is probably an item in the dial list for ISO speed, which selecting DX should set the ISO speed automatically.
Originally by user38978. Source · Licensed CC BY-SA 4.0
user38978
7y ago
0
Generated from our catalog & community — verify before relying on it.
DX encoding is a coding system on 35mm/135 film cartridges that lets a camera automatically detect the film speed (ISO/ASA). On the cartridge, the code appears as a pattern of conductive and non-conductive squares; cameras with DX capability read that pattern using electrical contacts in the film chamber. The same coding system also helped labs identify film.
It was introduced in the early 1980s, commonly cited as 1983.
To see if your camera supports DX, check the manual or look inside the film chamber for a set of small metal contacts where the cartridge sits. Many cameras with DX support also have an ISO setting option marked “DX.”
Compatibility is usually straightforward:
- DX-coded film in a non-DX camera: works fine; set ISO manually.
- Non-DX film in a DX-capable camera: works if the camera allows manual ISO setting.
- Cameras that rely only on DX, often some point-and-shoot models, may not handle non-DX film properly without a workaround.
So the key thing to know is whether your camera can manually set ISO if DX reading isn’t available or the cartridge lacks DX coding.
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