http://farbspiel-photo.com/
In this Hands-on Photo Tip, I will show you the basics of non-destructive editing. If you want to be flexible in your photo editing workflow, and if you want to avoid spending more time on an image than you actually need to, this is the way to go. You will learn how to do your edits such that
you retain full control all the time
you can create different versions of an edit and decide later which one to use and
you can blend edits with each other using layer opacity