You're right about it being hard to catch just right. I remember learning this (Way, way) back in high school when we were still on 35mm film camera's. Only played with it a couple times back then because it wasted so many pictures on a roll (limited to 24 or 36 shots per roll) and then having to wait a week until it was developed and printed at the FotoMat.
Nice job on these and like the comparison FAQs.