I am about to merge 4 LR6 catalogs into one "master" catalog. When I do this, will LR prevent thousands of duplicates?
Each of the catalogs has many thousands of the same photos. This was the result of not knowing what I was doing with LR some time ago. I want to create a single "master" catalog and then delete the old / original catalogs.
Thank you very much!
Lr will not create duplicate physical files in your computer, so no extra drive space is needed or used.
When you Import from another Catalog you do get an option to create Virtual Copies if there has been editing done in both catalogs to the same original photo.
Virtual Copies are not physical files so they only will exist as previews in the Catalog after the merge.
So the possibility exists that if you have developed one photo in several catalogs, then you merge all the catalogs to one 'Master' catalog, you might see several previews of the same photo, but there will only ever be one copy of the original camera file.
The benefits of merging to one catalog will be less space needed for the multiple Catalogs and Preview folders, less space needed for backups of the Master catalog only, all your editing and all files will be indexed in the Master catalog.
In addition to wobertc's response, I would suggest that you merge one catalog as a test so that you can go through the process and see the results. You may want to experiment with Stacking.