I don't get the hype about ND filters. Have better video without them. I used to think all the promotional talk was hired PolarPro agents hawking their product, but Oliver's comment above is fair.
They're a very useful tool for a specific job. But generally most mavic users tend to know almost nothing about photography and think they're do something totally different or a fix-everything solution.
Its quite simply, for VIDEO ONLY, if you have too much light a correct exposure is going to require a fast shutter speed. What video requires to look good to the eye is a slight blurring of moving objects from one frame to the next to it doesnt appear jerky. An ND filter if picked correctly reduces light so a lower shutter speed can be used so that some motion blur can be introduced.
This is only going to be useful for certain types of video - ones with movement. If you have a fairly static scene without much movement chances are you wont notice any difference at all if you use a fast shutter speed or a ND enabled slower shutter. However, if you have a scene with lots of motion such as flying low, chasing an object and so on then you will notice clear choppiness if the shutter speed is too high.
So, NDs are useful if its bright and the scene has a fair bit of motion in. Static scenes not so much.
For photos from a mavic perspective they're useless and actually detrimental. A photo generally you want crisp and sharp, you dont WANT motion blur or smudged details so you want that shutter speed as high as possible. An ND picked for the "correct" shutter speed for video, used on a photo will blur motion on that image creating a soft image which isnt the desired effect. This is also why taking a still from a video is unlikely to ever be as good as taking a photo of the same thing (even ignoring raw vs heavily compressed jpg etc).
Yes you can get around the blur by increasing the ISO but that the increases image noise reducing the quality.
Yes with land based camera you go for dreamy water effects and so on - even with an adjustable aperture to help reduce light those still require in the region of 10 stops (ND1000 to put it in perspective) to get the shutter speed in the region of 5 to 30 seconds. No such filter exists for the mavic (and you'd need even stronger due to the fixed aperture) and even if it did there is no way the little drone would stay stable enough for a multiple second photo to produce a clean image.
So in summary:-
(i) NDs are useful for VIDEO where there is motion in the scene
(ii) NDs are not that useful but also not really detrimental for VIDEO where there is no motion in the scene so may as well leave them on
(iii) NDs are detrimental and will degrade image quality for PHOTOS and should not be used.
Things they don't do at all:-
(i) selectively change balance of shadows or highlights
(ii) improve contrast
(iii) change the dynamic range of an image
(iv) improve detail
. Lower shutter speeds equal longer shutter openings and are more prone to blown out whites. This can be countered with adjustments to the ISO, but only to a point.
