Today’s Question: Will the new duplicate detection feature in Lightroom Classic help me find the numerous derivative copies of photos I’ve created and sometimes kept when I didn’t need to?
Tim’s Quick Answer: Probably not. The new duplicate detection feature in Lightroom Classic identifies duplicates that are essentially exact copies of the same file. If you created multiple derivatives individually from the same source image, none of those derivative images would be treated as duplicates.
More Detail: The duplicate detection feature included with the update to version 15.4 for Lightroom Classic can be incredibly helpful at locating duplicate copies of photos in your Lightroom Classic catalog. However, it is focused exclusively (at least for now) on identifying duplicate copies of the same image file, rather than near-duplicates such as derivative copies created from the original capture.
So, for example, if you send a raw image to Photoshop, creating a TIFF or PSD file in the process, those two images (the raw and the derivative image) would not be considered duplicates. If you had, on the other hand, managed to import the same raw captures more than once, those would count as duplicates.
Similarly, if you sent the same raw image multiple times to Photoshop and saved each result as a TIFF image with no actual changes applied in Photoshop, those images would not be treated as duplicates. If, however, you duplicated the same TIFF image multiple times on your hard drive and imported all those into Lightroom Classic, they would be treated as duplicates.
So again, in the context of the duplicate detection feature in Lightroom Classic, images are only treated as duplicates if they are truly copies of the same image file, even if they have different filenames. Derivative images that are different file types, different pixel dimensions, for example, would not be treated as duplicates.
I presented the duplicate detection feature in Lightroom Classic during my recent “Office Hours” session as part of my Lightroom Classic Ultimate Live Learning series. If you’re a GreyLearning Ultimate Bundle subscriber you can sign in to your account on the GreyLearning website (https://www.greylearning.com/users/sign_in) and then follow this link to view the recording of the presentation:

