If you see the same image in two project and not two different albums, you will have duplicate images.
Each image and all its version will appear in the same project, but can be used in many albums, books, slideshows, etc.
To decide which of the duplicate copies to delete, compare the dates and the size, so that you can be sure to keep your original high quality version. You may have imported lower resolution versions by reimporting from facebook or flickr, or imported additional previews or thumbnails.
Kirby Krieger's User Tip explains the different use of projects and albums beautifully:
Currently Being ModeratedMay 16, 2013 7:32 AM (in response to léonie)
Thanks, Léonie. I checked the versions (there are three) and all parameters are exactly the same and the image number is exactly the same. Does this mean I have three originals?
Ps. I've got Kirby's article, whew
I checked the versions (there are three) and all parameters are exactly the same and the image number is exactly the same. Does this mean I have three originals?
If they are in three different projects you have indeed three different originals.
When you delete two of them and empty Aperture's Trash, you should find two different original files in the Trash bin in the Dock.
Do you also have iPhoto?
If you have Aperture 3.3. or later and the corresponding iPhoto, you could open your Aperture library in iPhoto and use the programs to find duplicates in iPhoto libraries. For Aperture I only know "Duplicate Annihilator" and it is not free.
See Old Toad's post:
Currently Being ModeratedMay 16, 2013 8:08 AM (in response to léonie)
I do have Duplicate Annihilator but it ended up putting 3300 files into the duplicates after running and I just can't see that as right so perhaps I should try it again. But the iPhoto option might work as well.
Currently Being ModeratedMay 16, 2013 8:23 AM (in response to léonie)
Wow, it's a revelation! Now I see pictures by date, yea! Are the duplicates the photos that say copy or is that a different version? Sorry for all the questions, but I don't want to delete images that I've edited.
Are the duplicates the photos that say copy or is that a different version?
That will depend on your naming scheme when you imported the duplicate. But by defaultversions of an image will have "version" in their names. And edited images will show a badge, if you enable badge overlays.
In the example above the second image (from left) is an edited image and has the edited badge in the lower right corner. The third image is an aditional version of the same image - called version two.
You can enable the Metadata display from the "View" menu - "View > Metadata Display " and customize them (or from many more places).
Currently Being ModeratedMay 16, 2013 11:26 AM (in response to léonie)
Thanks! This has been so helpful today. I take it that I would want to keep the badge version and the additional version as they will be two different images connected to the Master. I will work on the library more and come back to you with questions, but thanks so much! I feel like I have a much better understanding now, which is incredibly useful!