Hello,
I am in exactly the same place as Vienna and am hoping to understand the situation.
I am wanting to simply have a library (gallery) where anyone/everyone can view the images inside it, but access to the "full image" is restricted to registered users.
I am aware of the "register_user" element of ZenPhoto (but being aware doesn't mean how to actually set it up) and I would hope to have visitors register using it, so like Vienna, my gallery would have registered and unregistered visitors.
I've looked at the Troubleshooting guide "Security" Point 4. and it seems like either:
(A) You set a single password to an Album and it's the same password for ALL visitors, registered or not (Published/password protected).
(B) You leave the Album unpublished, meaning that the Album is technically invisible unless you're logged in as a registered user (Not published/password protected). I assume the password protected bit means the "same password for all visitors" would still be in place.
This is different to what I'd have hoped - where a registered user would be required to add in their individual details specifically at the download full image point.
m.