1. Instead of putting the Christmas tree on Track 1, put it on trk2. Put sillouhette on trk1. Then depending on whether it's white on black or black on white and however you want the final image to look, on track two use either "luma" or "luma inverted" (looks black on white, so probably luma inverted) ---> Comp 1
1B. keep footage modes "normal." I'm not sure why you would change it to 'screen' in this instance.
2. Create New composition with the photo 2, in the same way as above, except with the exact opposite Luma from the first one ---->Comp2
3. Then create another composition and put both compositions in the third composition Comp1 on Track 1, comp 2 on track 2, (not sure if it matters) and then change footage mode of the top track to "add" ---->Comp 3
no need to export in between
Hope this helps
THANKS. I tried that originally, and it didn't do it. I'm guessing because the Tree Video is still there, it messes with each other. The b/w becomes negative and the color gets extremely dark. I played with color correction and tried to correct it. But, in the end I just simplified. I think my original way is neater, but the silhouettes stand out in this version the best. I always put up some small Christmas video each year.