Recently, I have really been working on maximizing the quality of video from my FPV tricopter (inspired by David at RCexplorer.se), and I found that the large amount of rolling shutter seen in the videos was coming from the exposure length. I built a real quick and dirty ND filter to try to lengthen the exposure, and it worked quite well, so I decided to try to build a nicer one on the cheap.
The only things you need are the ND filter, a thin water bottle lid, some CA Super Glue, and black spray paint (optional, but suggested). I purchased this 27mm ND4 filter on Amazon for under 5 bucks. I picked this size based on the sole fact that it was the smallest one I could find.
Next, I cut the water bottle lid along the top so that it had a diameter roughly the same as the GoPro lens. I’m using my GoPro without the case, mostly for weight and size savings.
As soon as the hole was cut, I smoothed it out and made sure it fit very snugly on the GoPro. There is not going to be any glue holding this onto the lens, so it’s important to make sure it fits very tight.
I then took it outside for some paint. Though it’s optional, I suggest painting the clear lid for two reasons: It will keep some light from entering behind the filter and degrading the quality of the image, and it also makes it look sleek and professional. Im using some flat black Rust-Oleum.
I sprayed a few coats just to be sure I had nicely covered all the clear. Lastly, I screwed the ND filter into the water bottle lid. I secured the filter to the lid with CA glue once I knew I liked the fit and placement.
I got lucky because my bottle lid was the perfect size, but if yours doesn’t quite fit, don’t worry. You can always just get the filter to fit the best you can and then CA glue it firmly in place. Note that there is NO glue between the whole assembly and the GoPro. There is only friction holding the two together.
And there we have it! A good-looking and functional GoPro ND filter for under 10 bucks! Below are a few clips using the filter. The blue color when the lens is in the sun is due to the first lid I was using being blue (and unpainted). I kind of think it added a cool light leak-esque flare to the video.