Camera Apps

iOS and Android phones both come with apps that take photos and record video.  But third-party apps, downloadable from your App store, can also use the phone's camera, and often have more features than the standard or OEM apps.  

For example, Open Camera is popular on Android.

By default, most mobile phone cameras use some form of auto-focus regime, to make photography easier for the amateur.  However, your phone app can likely change focus modes.  Experiment with different modes (there usually aren't many) to see which works best in keeping the lens focused on your work.