Sometime in 2018, my friend, Rob Kent, downloaded an Android app that would help him record analogue exposure information. The app would let you enter the aperture, shutter speed, ISO and a subject so you could refer to it later. He tried to use this app during a couple of our of regular lunchtime photowalks, but it was a pain to use. The app wasn’t very user-friendly, it never “remembered” any of the settings from previous entries requiring all exposure data to be re-entered for each shot. This meant that recording a shot took way longer than necessary and, in my view, put you off using it. At the time, I was using a pen-and-paper approach to record my shots and was finding that to be equally slow and cumbersome. After trying the above app myself I thought: “I can do better than this”.
The Petri 7s is a manual, fixed lens rangefinder camera typical of the 1960 and 70s. It has a 45mm f/2.8 lens; a maximum shutter speed of 1/500 of a second plus, a built-in selenium light-meter. Keen to try a fixed lens rangefinder style camera I ended up buying three and managed to get two working examples.