I do not normally feature paid apps in my App Tour galleries but this one is so fast and accurate that I felt it was OK to tell you about it even though it costs $2.99 to purchase. By the way, if you have a lot of images to clean up then it is a very well spent three bucks.
The premise of the app is very straight forward. Tell it where your images are stored and it will scan across those directories to find out which ones are duplicates.
To give you an idea of its scanning speed I set it up to look over 5.5GB of images and the scan was done in less than 45 seconds - that included nearly 5,500 files spread across over 800 sub-directories.
The app does not just use the images file name or directory to determine its duplicate status but also performs a binary comparison to verify it is an exact duplicate.
Once the scanning process is complete you then review all the duplicates and decide which should be marked as the original and then all of the duplicates will be moved to a directory labeled PhotoDuplicates. Those duplicates are not deleted - just moved to this directory - you can then decide on which ones to retain and which to delete permanently.
The entire process is just four steps as you will see in the gallery of screenshots for the app.
Download the Ultimate Duplicate Photo Finder from the Windows Store.