Smart phones are great for recording your swing, and here are a few ways to optimize your camera settings for best results...
1. Switch your camera to its highest frame rate (slow motion) and resolution possible.
2. Have the camera at hand height when addressing the ball.
3. Try to have the camera 15'-20' away.
4. Record your swing from 2 angles...
From the "down the line" view, place the camera directly behind the hands pointing at the target.
From the "face on" view, place the camera square to your stance.