Thanks for the clarification Steve. Once I wanted to see my test strips with one full stop steps I calculated this series of exposure times for 5 sliding positions of the sliding darkslide cover: 40, 20, 10, 5 and 5 seconds. That gives me stripes exposed as this: 5, 10, 20, 40 and 80 seconds which covers the entire range of most of the negative I should encounter. Then I do a second test strip to fine tune my selected time. Maybe 2.8, 5.6, 11, 22 get closer to the actual curve of the paper, but in this case shouldn't we also apply these time steps with our cameras?