Where did you see that quote?
The normal behavior of Lightroom is to exclude duplicates, assuming you have that option turned on. Sometimes it may get turned off by accident. For a photo to be a duplicate, it has to have the same capture date and time, same file size and same original file name.
Thank you. Yes, I read that in the documentation. The quote came from pg 133 of the 7/26/2016 version of the LR reference manual. I'm using LR 6.0 downloaded from Adobe site within the last month.
The 'gotcha' must be the file name, since I'm importing from files already saved, the file names are obviously distinct. I was guessing the 'same original file name' refered to what the camera wrote into the meta data. However, the only thing I see on LR panel is 'file name', not 'original file name', and of course that matches the non-duplicate name from the file system. The names suggest that some previous photo tool (iPhoto, Picassa, or Photos) replaced the meta data to match the file name when it was written.
If most of this is correct, then I guess I need to rely on a third party tool to remove the duplicates? Last one I tried using on a Photos library corrupted the library causing me to embark on this laborious process of recovering and reorganizing using LR.
The quote you provide is not as clear as I think it should be, but it seems like it is saying that there is no tool to detect duplicates that are ALREADY imported. Lightroom certainly can detect a duplicate if you are trying to import a duplicate of a photo that is already in Lightroom.
Yes, I think you need a third party tool at this time.
Note: The Synchronize Folder command does not detect duplicate photos in a catalog. Lightroom does not have a function that identifies duplicate files.
This statement in the Adobe help is incorrect. dj_paige's reply explains the actual behavior.
I filed a bug report on incorrect documentation: Lightroom: Misleading documentation on duplicate detection | Photoshop Family Customer Community . Adobe is usually very good about fixing documentation mistakes reasonably quickly. Thanks for calling it out.