So here is an interesting story for you:
These two photos were taken about six months apart. I had a roll of film in the camera that I actually forgot about. When I shot the rest of the roll, I assumed it was ISO 400. (No, I didn’t label it, thank you…)
When I finally completed it, I realized that it was actually ISO 50, and that the last six pictures were at least 3 stops underexposed. The worst part is, I couldn’t remember whether the first six pictures were the ones worth saving, or the last six. As a result, I stand-developed them in Rodinal 1:150 (1 hour) and actually ended up with usable images on both ends of the roll. Here are two examples–both summer and winter.