Syncing Photos from iPhone 5 to iPhoto on Macbook Air

I have synced my photos from my iPhone 5 to my Macbook Air through iPhoto to free up storage. I do not have a single picture in my camera roll, but on my iPhone in storage settings, it says that Photos and Camera are still taking up 7.2GB of memory (Specifically: Photo Library - 7.2GB, Synced from iTunes Library - 0.7 KB, and Shared Photo Stream - 4.1 KB). How do I completely delete this photos off of my iPhone to free up storage without erasing them from my iPhoto on my Macbook?