Hi, I am looking for the possibility to show up the Lightbox only for registered users and deactivate it for no logged in visitors.
I am using Watermark on articles, and because the Lightbox shows the original image, with no watermark, I would prefer to be accessible for registered users only.
Leo, try the rl_lightbox_args filter hook. It passes a couple of arguments that enable modification of the lightbox output but this could be used to remove the lighbox for certain users (logged in for example).
But it will not remove the image link from your theme. It will just link to the image file without applying lightbox.
I think the solution for you is to modify the theme to output image links for logged in users and images (without links) for all the others.