Excuse my lack of knowledge, but what do filters actually do for the camera?
Filters are an additional way to control the amount of light that hits your cameras sensor.
ND = Neutral Density. The darker the filter the less light it lets into the lens. ND simply reduces the amount of light, ND filters don't change any color balances. Think of ND as car window tint.
There are 3 ways to change the amount of light that hits the sensor of the camera:
- Shutter
- Aperture
- Filters
All 3 will give different results, and all 3 affect each other.
The aperture is a physical ring or collection of blades that open and shut in the lens. Basically; the more open the hole the more light hits the sensor. The smaller the hole, the less light enters the lens and onto the sensor. This is measure in "f-stops". The lower the number, the wider the hole. Higher number = less light (a bit counter-intuitive, I know). The Mavic's "f-stop" is a set 2.2 (quite wide open).
Shutter is electronic and not directly related to the amount of light actually entering the lens/hitting the sensor.
A filter reduces the amount of
total light available to the camera's sensor. The aperture cuts light out like a sun-shield but doesn't actually reduce light intensity and the shutter controls how long this light hits the camera's sensor.
There's also ISO but that's a sensitivity setting, not "amount of light" coming in from the outside world setting.
A real world example of filter usage would be a super bright sunny day, no clouds in the sky. Your camera's lens only has a finite ability so you could add an ND filter to further reduce the amount of super bright sun. NDs help with stopping images and video looking washed out or over-exposed.
Obviously, you wouldn't benefit from using ND at night, or where you can control the actual light source.
