I did successful (carefully checking the pattern among the 1000s of dups found) find and deletion of dup images. However, when I tried to refine focus on pair of image folders, I got list of "duplicates" that showed exact same filepath for each file. It's hard to see small differences in pathname, so I confirmed by looking carefully and by revealing actual file, labeling it and confirming its location and then revealing its so-called duplcate. They were EXACTLY the same file, just listed twice. I set up safe deletion and did two tests to see what would happen if I let decloner manage them. I have pref set to leave an alias behind (which did not seem to work with "delete selected" but did work with "delete marked"). I did a manual and a delete marked. In both cases, the only copy of that false dup file was deleted and no alias left behind. Even though the files were exactly the same, decloner chose one as "oldest" or "newest" and would delete--even though exactly same file, so no timestamp diff.

My big worry is that I didn't check previous deletions as well as I could or that decloner may have deleted some non dups.