Making flying videos with the GoPro: Getting rid of the floppy propeller

The Gopro is an amazing little camera. We have had one for a few years now, and have used it everywhere, from biking to swimming and snorkeling, and of course, when we fly.

Even if you haven’t heard of rolling shutter issues, you have most likely seen this effect. In our case, the problem is with the propeller, that appears as a banded, wriggling structure, and is quite distracting.

There are several approaches to fixing the problem, one of which you can see here. If we only wish to address the strange propeller, the solution is quite simple. In essence, the issue is that cheap cameras such as the GoPro, do not have a physical shutter, but control the aperture synthetically by electronically rolling the sensor sensitivity, thereby mimicking a mechanical shutter. The only way for the user to control the rolling shutter speed is by changing the available light. Limiting the incoming light with a neutral density filter is very useful in improving the rolling shutter effect.

I thought it may be helpful to present my solution for fitting the filter to the GoPro, which seems to work well, and could easily be adapted to other cameras.

I purchased a second camera case, as this is a semi-permanent solution, and I wanted a dedicated case for the cockpit. Using oven-cured clay, such as Fimo or Sculpey, I made a collar that is attached to the black ring that holds down the outer lens. The most challenging part was finding appropriate screws. I was fortunate to find several in my scrap-bucket which work well.

The filters are about the largest that it is possible to use

The screws are very close to the back surface, but seem to stand up well to use

Another view

I used 2 stacked 58mm neutral density filters. The lowermost filter is embedded in the clay, while the uppermost one can be removed. The filter did well when repeatedly baked in the oven. Fingerprints are an optional security feature!

The floppy propeller is (mostly) a thing of the past, as you can see in the video above.

The solution is both ambient light and propeller-speed dependent, so there are times when things are not perfect. The main problem with this method is that the lens is too small, and there is an element of vignetting. This is due to the design of the GoPro camera body limiting the filter size that can be used. Given the GoPro’s amazing field of vision, this is solved easily by using a video editing application to zoom in slightly. Using Cinelerra, I found that changing the Z-axis of the camera in the compositor from 1.0 to 1.15 improves the vignetting issue nicely.

Due to the filtering, the video becomes quite grainy in low light, as is to be expected. Light is seldom an issue when flying, but it is noticeable at startup early in the morning. Once in the air, there always seems to be enough light to eliminate this concern.

Hopefully some of this information is useful to others out there. If so, please leave a comment and/or a link!