Backup item in storage space - How can I free that space up?
I deleted an ungodly amount of pictures stored locally on my MacBook that had also already been imported on iPhoto, thus taking up unnecessary storage space. I deleted around 15 GB and that was indeed reflected in the decreased number of gigs under the label Photo on About this Mac -> Archive. However I noticed that in turn, the Backup item increased accordingly. I restarted the computer assuming it would clear up all deleted files once and for all, but Backup is still 17.7 GB as per the picture (I'm Italian and so is the language of my laptop), and it was only 2 or so prior to deleting those image files permanently. How can I reclaim that space? Where are all those deleted files that seem to still be clogging storage? Thank you for your help!
MacBook Pro, OS X Yosemite (10.10.1)