In 'Pro' mode and set to Manual on the Action 6 the user has good control of exposure settings, so can set a preferred shutter speed and ISO value, to preserve natural motion blur, but, unless light is particularly poor, the 'footage' is very likely to be overexposed - and that is where ND filters can save the day!The ND filters can reduce light onto the sensor by up to 8 stops, giving a lot of flexibility - in manual mode the camera display will tell you the exposure in + or - EV (1 EV=1 stop) so selecting a filter that keeps that value between -1 and +0.7 should end up giving natural motion and well-balanced exposure. (I shoot in D-LOG-M and use a video editor to grade the footage, and assist with minor exposure variations)The CPL filter can assist in reducing reflections on surfaces as well as getting 'cleaner' colours in sunny situations - just like polarised sunglasses!Black Mist 1/4 can be quite subtle (photo below) in softening the image as well as desaturating colours a little - but can pick up and 'glow' specular highlights very pleasingly - experimentation is recommended, if only as it can be great fun!K&F CONCEPT, in my opinion, have nailed it once again in providing very good quality (no noticable colour cast with any of these filters) filters that are quick and easy to use, and will assist in producing better photos and video with the Action 6, at a price that isn't too prohibitive.