How does Content compare work in FreFileSync

[Jubliano]

I am new to this App so forgive me If I am misunderstanding something about FreeFileSync.

I have many photos on my D: drive - "D:\1. To 160918 Do Not Add Files\1. Photos\Make Mod year dir"

I also have an older backup on a My passport Drive "H:\1. To 170918\1. Photos" - I know the directory dates are different but I thought FreeFileSync checked files).

When I run FreeFileSync on these two directories using content compare – because I know some of the files will have different names but the same content – more on why later if necessary, I get far more “unsysnced” files on D: than I expect (ie on H but not on D).

So I copied one of the unsynced directories (using “open with explorer” from within FreeFileSync) to another directory on D called "D:\PA from olym".

I then used AllDup to compare "D:\PA from olym" with "D:\1. To 160918 Do Not Add Files\1. Photos\Make Mod year dir" using File content byte by byte compare. I get many duplicates with this - in fact every file is a duplicate.

So I am confused, I thought both programs are looking for duplicates – All dup shows them. FreeFileSync shows the non duplicates.

Clearly I am wrong with this assumption. So can someone explain why FreeFileSync tells me files do not exist on - "D:\1. To 160918 Do Not Add Files\1. Photos\Make Mod year dir" when they clearly do.

I have also confirmed this from within explorer.

Attached some screen dumps if that makes my complicated text any clearer.

Any explanation would clear my befuddled mind and be gratefully received.

[Plerry]

FreeFileSync (FFS) is a sync-tool and not a duplicate finder for duplicate files under different names or in different locations.
When using the Compare by Content option, FFS "only" compares the content of identically named files in identical positions in the file directory-tree, relative to the root of the left- and right-base locations.
This, in order to evaluate the need to sync a file or not.

[Jubliano]

Thanks Plerry
Crystal clear
Regards