If the permission of the photo is not set in Public (Me Only, Members, Friends), Anonymous or unregistered person should not be able to see the contents of the photograph.
For example :
https://www.insoler.com/m/photos/view/14938239411183
We'll see an "ACCESS IS FORBIDDEN" error message.
But if there are other members who copy photo's URL, they can be posted on the forums or other websites ! Like this:
8fd881eb2fc31ca205581c9b42484a85.jpg
To maintain the same "permissions" in the album, there should be no other way to see the content of a non-public photos.
I suggest replacing a photos without permission to browse.