Why does my iPhone 4S keep saying there's not enough storage?

My 16gb iPhone 4S keeps popping up with a little box saying there's not enough storage every time I try to take a picture. I'm travelling atm so not being able to take pictures is pretty annoying.
I have previously deleted loads and loads of things to make room for all my travelling pictures and I just don't understand. I've tried resetting it, is there anything else?

There's not enough storage? Duh

If you go in settings, go to general, go to usage. From there it will tell you how much room you have on your phone and how much room your apps are taking up. It will show each app individually. I also find videos take up loads of room! Maybe you should try emailing some pictures\videos to yourself so you can delete them off your phone and once you get home you can download em on your computer. Music also takes up a lot of room if you delete all your music once you get home you can download them again via iTunes? Have fun traveling