Replying to What to charge?

This past week I got an opportunity and asked to help a filmer with video shoots and possibly with the editing process. Yesterday I went in and filmed with him for about five hours, he asked me what I thought my compensation should be and I wasn't quite sure so I said I'd get back to him.

To give you an idea he's making somewhere between 2-5 grand for each video and they come up about once a week (it's looking like this). What should I charge him for just a full day/ half day of shooting solely for another camera angle in the editing process. Anyone else in a similiar situation and want to share what you charge?

thanks!