I’ve just acquired a Horseman 6x9 roll film holder and decided to head out at dawn to try it out, two hours and almost 2 rolls of film later I finally noticed I had my light meter set to ISO 400 instead of 50 so everything except the last couple of shots will be 3 stops underexposed

This got me thinking and I started to wonder what silly mistakes others have made, sharing them might help me avoid them

So, go on, fess up.
Paul.