This app was mentioned in 9 comments, with an average of 1.33 upvotes
If you're at all serious about taking decent shots and want to be able to fiddle around in post, AZ Camera comes free out of the box with the ability to shoot RAW. It also has a pretty straight-forward UI that's pretty easy to get to know. (And you can edit RAW on your phone with Google's free Snapseed.)
One disadvantage, and this may only be my unit, or the current build: when I first launch it, it can't seem to connect to the camera. So I switch from back camera to front, and back again, and then it works.
https://play.google.com/store/apps/details?id=com.hecorat.camera
Try that, someone in /r/android said it works for the S6 and it is awesome on my Nexus 6. The live readout of White Balance, ISO, and Shutter speed are awesome
https://play.google.com/store/apps/details?id=com.hecorat.camera
That's the one.
Use this app here https://play.google.com/store/apps/details?id=com.hecorat.camera If you adjust the ISO and WB, (White Balance) you will get much better photos
I use AZ Camera on my 5x. It's free and there's a paid option for more features
AZ Camera - free, and tons of manual options