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DX Encoding

Happy 2017 everyone!

One of the fun parts about this project is all the “light bulb” moments I get when I figure out a mystery. I’ve become so digitized the analog world seems to hold a lot more mysterious tricks up it’s sleeves.

I was out shooting a roll of Fuji 400 135 film the other day with my Pentax P3 and I realized I hadn’t set my film speed on the camera. I was looking all over the camera and quickly came to the realization there was no where you could set it. This seemed pretty unusual considering the Pentax P3 has a built in light meter. How did the light meter think it was calculating shutter speed correctly without having a film speed set?? That was kind of blowing my mind for the rest of the shoot.

Once I got home I looked up the manual for the Pentax P3 online and read something about keeping the DX information pins clean. Turns out those black and bare metal squares on your film canister are actually a barcode for automatic cameras and photofinishing machines. There are 12 metal pins inside my Pentax P3 that read this code electrically to determine film speed on line one, number of exposures on the first 4 segments of line two and exposure tolerance on the last two segments of line two.

The photo I’ve added shows the inside of the P3 with 12 tiny little pins next to the canister of film beside with the DX encoding shown.

See this link for more information https://en.wikipedia.org/wiki/DX_encoding

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