Do a search for Mavic Pro Filter and you will get a lot of information. Generally: ND4 for low light (sunrise/set), ND8 for cloudy days, ND18 for sunny days, ND32 or 64 for bright snow or sand. Polarizing filters are fully effective only if you have them oriented correctly to the sun. It is generally recommended to use non-polarizing filters for video since the sun angle will change as you pan making items like the sky lighten and darken as you pan. This makes it more difficult to maintain a constant sky in an edited video.