Hide image title for unregistered users

[mkern]

I need to hide the image title for unregistered users is there any way to do this?

[Αndré]

Image titles are displayed below thumbnails and the intermediate-sized picture (and maybe are used as page title, I haven't checked that yet). Is there restricted access for unregistered users? If so, code modification can be reduced. Please also post a link to your gallery.