I am an android novice. My question is : Is there any free app to take pictures or videos using any phone key, like power or volume up/volume down, without touching the screen button? I checked the other answers here, but they talks about cyanogenmod or a paid app.
There are many apps. You can go with Vosco which is my favorite one but without key mapping (no hardware button to take pic) but a great one. Otherwise, Camera360 is a good choice. Also you can go with CameraMx (or Mx Camera maybe) or Line Camera or Cymera (this one has a great range of photo editing tools as well). All of these can be customized to take pictures with volume key or so.