This app is a real saver and game changer, I've tried it myself, and I've seen significant changes in every single photo; it enhances images like:
Very low-->Low Low-->Good Good-->Great Great-->Perfect and so on...
This app is Remini, and they do have free service (by watching an advertisement while the file is prepared)
But it limits you to 5 photos per day using the free version; however, most probably, you want to have to enhance 5 pictures each, and every day, you'll need it only for specific photos that you want to look great.
Go ahead, install Remini and try out this great tool, and make the best out of it.