I have to say, I soon got fed up with test strips, contrast adjustments, enlarger height compensation and bought an RH Analyser Pro. It has a little bit of a learning curve to get the "feel" of where to take the measurements, and is not cheap, but........virtually zero wasted paper these days and a very high proportion of prints I am happy with 1st time. It's also a real education tool because you soon see how time and settings change if you alter the contrast or change to a different paper. I am sure if I had persevered with just using test strips, I would have become much better at interpreting them, but I got impatient!