My iPhone has too much data stored on it, but it won't unsync the data either
So the time has come after taking many pictures, and downloading many apps, that my iphone has too much data on it. So I want to clear up some space inorder that I may continue downloading new apps and taking new pictures. I've decided that the first things I don't need synced to my phone from my Mac would be the pictures stored on here (the mac) and the podcasts I've already listened to. BUT when I unselected them from itunes, I just get a message saying something along the lines of "Won't sync, there isn't enough space" (and then it proceeds to tell me I need 308 MB of extra room). I've tried everything I can think of, but I still don't know how to unsync my 3.6 GB worth of extra pictures I don't need! Can anyone provide me with some insight in how to go about doing this?
EDIT: This error message is coming up while I have my phone plugged into the computer
iPhone 4S, iOS 6.1.3