Follow up to my earlier post criticising Duplicate Annihilator:
After checking YouTube, I decided to try the free program called Duplicate Cleaner for iPhoto.
It works!
First point it to your photo library "Pictures". Mine contained around 57'000 photos of 218 GB. First it ran a scan to find "potential" duplicates. It found around 8000 potential duplicates. It then re-examines those potential duplicates looking for "exact" matches. This second pass reduced the number of duplicates to around 7000. The space used by the 7000 duplicates was about 12gb,
These two comparison processes took a couple of hours, but I could see the progress, as it kept a track of how many photos were checked, and there was a progress bar too. This was reassuring as it meant that I could see the program was working.
After the second pass, it displayed a list of duplicates in the form of icons, with the original on the left, and the duplicates on the right. All thumbnails had a check box. The check box on the original was un-checked, whilst the check-box of the duplicates on the right was ticked. The check box was to move potential duplicates to the iphotos Trash folder - if I confirmed.
You can press the down arrow to review each photo, and its duplicates one after the other. A visual inspection tells you the photos are identical, but you can also see all the other data, like name, date, time, file location, event name, file location (in masters), and so on in case you doubt the photos are identical.
Not only did it find duplicates with exact name and date/time match, but it also found duplicates taken without any date or time information, and which had different names, e,g, "Pic8923.jpg" and "Photo_of_my_cat.jpg". In this case the second photo - the duplicate - called "Photo_of_my_cat.jpg" was checked for potential deletion. If I wanted, I could have changed that and deleted the original, keeping the duplicate.
I could not check all 7000 duplicates metadata, but it was fairly quick to scroll through them and check they were visually the same photo. I still as a precaution checked the metadata on several hundred photos to make sure that I was not deleting a 2mb photo and keeping an 11kb thumbnail. As far as I could tell, there were no photos of different sizes which were claimed as duplicates.
I could not find any photos marked as a duplicate wrongly. I have many photos with the same name and I was worried that two completely different photos both called "Dad.jpg" might be classified as duplicates. This didn't happen.
The last step was to click the box "move duplicates to iphotos trash". This started a process of deleting the checked duplicates one by one. This seems to be the slowest part of the process. It is still proceeding to do this as I speak. It has deleted a couple of hundred photos so far over around 30 minutes. It deletes about 10 photos a minute, so the 7000 duplicates will take around 700 minutes or over 10 hours. This is kind of slow, but in another sense it is reassuring because I suppose it is doing the job in iPhoto correctly. The main thing is that once again I can see the progress, so I know that it has not seized up on me.
Although the deletion process has not finished as I write this, everything looks like it is going smoothhly, so I rate this program, Duplicate Cleaner for iPhoto, as excellent. It's free, intuitive to use and intelligent enough not to make mistakes with false duplicates. I found a demo of how to use it on YouTube.
My only criticism is that it won't find smaller versions of the same photo. So for example if I have a photo of 1.7MB, and a smaller copy of 250kb, I would like it to be able to find these two and offer me the chance of deleting the smaller photo. Nowadays with large hard drives you don't need smaller copies, but it was a feature of some Sony cameras a few years ago to make both large and small versions of each photo.
