If you haven’t done it yet, you will. Your camera, lovingly loaded with 100ISO colour print film, turns out to be 400ISO black and white when you finish the roll and open it. Or not loaded at all. Or you load and shoot the same roll of film twice.
Back before the last ice age, I worked as a chemist. Not the dispensing kind – I was the model for Beaker. I worked in a quality control lab within a manufacturing business, so we were processing multiple large batches of samples every day. One soon learned to label everything. My favourite tool was an ancient fat propelling pencil that took a wax insert that would write on glassware but was water soluble so it was easy to clean off.
The habit carried-over when I switched to working in IT. I did some big office moves and became a label fundamentalist.
Speaking of habits, my grandad used to say that a habit was a good servant but a bad master. He also used to iron his socks, so make of that what you will.
Labelling is a good habit though. But I can’t really write on my cameras and hope to wash it off afterwards. So I use tape.
I tried using the paper-based masking tape, but this stuff resists being written on and falls off when you are not looking. So I use electrical tape. My dad was an electrician, so I was brought up on fluff-covered rolls of gooey black PVC tape. That stuff is the opposite of useful for labelling. What I found in my local hardware shop is white electrical tape, which is perfect. The glue doesn’t smear and the tape releases cleanly without leaving a sticky patch. I can write on it with a marker or ballpoint.
So what I do is label every camera that is loaded with the film it contains. When a film is taken out of a camera, the label moves to the film container. If I’m developing it myself, the label then moves to the lid of the tank. If I remove a film part-shot, the label will show how many frames I’ve used.
I am delighted to say that I have not fupped a single duck since I started doing this. But, as I learned in IT, make something idiot-proof and the idiot gets upgraded. I may not mistake my films any more, but I have moved on to greater things and discovered many new and interesting ways to fail.