groucho, Can't tell if you're trying to get shadows on the HDR or on a backdrop image... Could use a glimpse of what you are trying to map shadows onto, though. From what I can see in C3, you have the HDR image in the background and that can't really catch shadows. I'm going to try to see if I can't generate a test for shadow catchers. You may have to add a neutral backdrop and key it out in another app... Something I'll have to look into. Glad you got something out of it! Ken