Every once in a while you find a tool that is just great at doing what it does. It takes very little system resources, might not even require an install, and works as fast as you can reasonable expect the task to be done. I found one such tool for removing duplicate photos.
Duplicate File Finder is the latest find of mine to go in this category. It doesn't require and install, is free, and quickly scanned several thousand photos, and then showed me the path names of each set of duplicate photos, allowing me to choose which ones to delete. It was a bit tedious to do the selecting, but I think manually doing that is the only acceptable way given the dire consequences of accidentally deleting the wrong photo.