If, like me, you prefer to use manual settings with your action camera (or any camera for that matter) you’ll need neutral density filters to control light when shooting at lower shutter speeds and/or wider apertures (f-stops).

The need is especially critical when shooting video in order to preserve the 180-degree rule* which prescribes a shutter speed of twice the frame rate. So, for example, if you like to use the “filmic” 24-frames-per-second, then you’ll want to maintain a shutter speed around 1/48 sec.

Maintaining our camera’s native ISO (say, 100) works in our favour here to avoid the noise that comes with higher ISO. But if we wish to use a wide lens aperture to blur background and isolate the subject (talent or merch) then, combined with relatively slow shutter speed, we’ll likely run into the limitation of overexposure.

So, we need to restrict the amount of light reaching the sensor (or film). ND filters to the rescue.

I have a comprehensive Nisi filter system for my mirrorless and DSLR cameras but, of course, they are not compatible with something like the GoPro Hero8 action camera “Mrs. Claus” bought me for Christmas.

It never occurred to me to control settings on my previous, 8-year-old Hero2 camera … because early iterations provided no way to take manual control. As illustrated in my previous GoPro Hero8 video post, we now have control over shutter speed, ISO, frame rate, white balance, bitrate, colour profile (I use flat), and we can choose from digital fields of view, including Linear FOV that banishes the extreme wide angle lens distortion common to most GoPro video footage.

In short, I can now create “cinematic” clips that more easily blend with footage from my full size hybrid cameras.

*Not to be confused with the rule of the same name that refers to keeping talent on the same side of the screen throughout a scene, here we are concerned with creating the “filmic” look in video that we are used to in cinema. Maintaining a shutter speed twice that of our frame rate, particularly when that frame rate is 24fps, introduces just enough blur to keep video footage from looking, well, like video footage. A few digital filmmakers have experimented with faster frame rates (up to 60fps), but the reception has generally been unfavourable.