Why do you need filters? It's a valid question, of course, who hasn't asked themselves that? I think everyone has stumbled across this topic and this question... The answer to this is very simple and surprising in view of this video - no, you don't need filters on a camera, it works without them... but it would be more of an advantage than a disadvantage which to have and use. Anyone who works a lot on the water and beach, like me, or of course, like most of you, vacations there, quickly learns to appreciate filters. First, they are a very good protection against dust or sand from the beach. Of course, a filter also protects the lens, the lens in the camera. So much for the obvious, but the main job of a filter is to let less light through onto the sensor, it's like putting sunglasses on the camera. This has the advantage that you can get longer exposure times. It helps the camera to adjust and react faster in automatic mode when controlling the exposure time or white balance. Or if you prefer to work in Pro mode, you will quickly find that the exposure, the shutter, generally works better.
In general, filters make the water smoother, and there are also fewer reflections. Or if you take great landscape shots, the sky immediately looks a little bluer. Filters also enhance the colors generally, making them more vibrant. DJI has, in my opinion, excellent colors and in connection with a filter, the recordings are made automatically. This saves you having to color the film material because it comes out of the camera almost finished. Of course, the full professionals among you have other requirements and such, but I'm speaking here for the normal user, like you and me...
There are different ND filters. It starts **in my set at ND 4 and goes up to ND32. The ND4 filter lets only ¼ of the light through to the sensor and the ND32 filter 1/32. I use my filters like this... morning ND4, midday ND8, noon to afternoon ND16 and afternoon to late afternoon when the sun is very high ND32, and then in the evening just before the golden hour I go down again with the filter strengths. Over time you will get the hang of when and where which filter is best used is not witchcraft, even if many would like you to believe it.
Especially in summer or in winter when there is snow, I think it should at least be almost mandatory to have ND filters with you. If you like to film in Pro mode and work a lot with it, it is almost a must to work with filters alone because otherwise you cannot work with exposures in a meaningful way....