As explained here, "gphoto2 only as root -" https://lists.fedoraproject.org/pipermail/users/2014-January/446166.html with the reference, "systemd-logind not tracking startx sessions" https://bugzilla.redhat.com/show_bug.cgi?id=806491 Applicable to Fedora 19 - 21 & Rawhide.
Created attachment 916668 [details] startxfce4 & systemd-logind harmonization
Applied to rawhide and f21. Thanks! If there's a need can push it to older releases as well...