I agree with using the Kodak numbers as a starting point. However, one advantage of the dichro head is the ability to use values in between the stated grades. For instance, Ilford gives grade 2 1/2 as 5 magenta, and grade 3 as 30 magenta. But, I find a lot of my negatives need 10 magenta. Yes exposure times change. You will have to do new test strips at the new filter setting.