Thanks so much T Paul !
And all the other very useful tips and/or advice by Ro, Ed, Duv all Masters from my beginner's point of view. !
I do use curves more often than levels, though -up to now- I did not quite understand the fundamentals of either. I read the article in the first link about curves and the meaning and results to be obtained from all of the options and agree with Duv's description "WOW !!".
Rgds - Martha