I have one question, but it doesn't need a new thread. I metered f/22 4 sec. iso 5. After a lot of testing of different exposure times I ended up using 8 minutes exposure time when metering f/22 4 sec @iso5 to get a decent exposure. Is it correct that I need to calculate my exposre using about f/2800 iso5?

I read somewhere that the iso for paper is about 5, but it doesn't make sense when I needed 8 minutes exposuretime.