I somehow imported everything into Lightroom twice - how can I undo this?

Question

I have somehow managed to import a large number of images from my camera into Lightroom twice. I would like to know how to undo this, removing all the duplicate files. A previous question on a similar topic is answered by a commercial plugin, but this seems like something that should be possible within Lightroom itself and I don't really want to install untrusted software or pay £8.50 to do such a simple thing. So this question is whether this action can be achieved without purchasing extra software.

In case it's useful, here are the details of where the duplicates came from. I'm a completely new user of Lightroom. The first time I used it, I imported all the images into Lightroom from my camera, without deleting them. The second time, I tried to import the new images, but it started importing all of them a second time. I'm not sure why it did this, since the photos I'd already imported were not checked. (They were greyed out and could not be checked.) After a while I realised this was happening and stopped the import, and then after that I went into "last import", selected all the photos, and deleted them. I then went through the import process a third time, and this time it seemed to just import the new photos. However, after editing the new photos for a bit I've realised that the old photos are still in there twice after all.

Answer 1

1. From the Library view, click on All Photographs in the Catalog pane.

   

2. Down at the bottom of the window, change Sort to "Added Order":

   

   If you don't see this, press T to show the toolbar.

   Alternately, select View → Sort → Added Order from the application's main menu.

3. Click the first duplicate photo you imported, then Shift-click the last one, which should be the last photo in the grid, if you haven't imported anything else since.

   You could also do it in reverse, if you prefer: click the last photo in the grid (assuming it's one of the duplicates) and then scroll back up until you find the first duplicate and Shift-click that one.

4. Press Delete, or select Photo → Remove Photo... from the application menu.