Does ND filter on GoPro cameras actually remove jello and make your FPV videos look more cinematic? We are going to find out in this post, and I will also explain what an ND filter is, and how ND filter affect GoPro image quality.
Further Reading: How to choose an HD camera for FPV
What is ND Filter?
ND stands for “Neutral Density”. Ideally, an ND filter can equally (or neutrally) reduce the amount of light across the entire spectrum entering your camera sensor without changing the image color. In a nutshell, it’s a pair of sun glasses for you camera! :)
Here is an example of before and after applying an ND16 filter on my GoPro Session.
From my understanding, ND filters are often use in high light situations, where you are unable to lower shutter speed. This creates realistic motion blur and reduces jello (vibration in your video). However it’s not as useful in dark environment as it lowers brightness.
In this video I tested ND4 and ND16 filters under the same lighting condition and see how they affect the image quality.
ND Filter Removes Jello?
As you can see from my testing, ND filters can indeed reduce the amount of jello in the FPV footage. The higher degree the filter, the more effective it is.
The key being the motion blur that ND filter introduces.
Vibrations (jello) can be taken out by introducing motion blur on the edges of the frame, whilst keeping the center in focus. This replicates what happens with our actual eyeballs, since only the center of our vision is in focus, moving at high speed like when driving puts our peripherals in blur, with our focus on the road being clear.
Shutter speed on the GoPro is automatic by default, brighter sunlight will shorten shutter speed otherwise the image would look overexposed. Adding an ND filter slows reduces the amount of light that enters the camera, which leads to slower shutter speed and thus less artifacts and jello.
Jello effect can be caused by many reasons, such as badly tuned PID, and bad motors bearings. Even if you had done everything properly, one bent propeller is enough to make your drone oscillate and ruin your FPV video!
It’s impossible to make sure your quad is perfect in every flight, that’s what makes ND filters so powerful for minimizing jello on your GoPro camera.
ND Filter = Cinematic Video?
There are a lot of talks about how ND filters can make FPV videos look more cinematic. I guess it depends on what the definition of “cinematic” is. My observation is that ND filter introduces more motion blur to the footage, and that video effect is very special and unique.
It’s important to shoot your video at 24FPS to 30FPS in order to bring out that cinematic look. Even if you shoot your video at 120FPS, if you slow it down four times to 30FPS then interpolate frames to eliminate stutter, it would looks very different.
Similar effect from ND filters can be achieved when filming at sunset. Because of the low light environment, the camera has to lower the shutter speed in order to capture enough light for the footage to not look too dark. And the lowered shutter speed can cause motion blur. Perhaps this is what helps to reduce jello too.
By using ND filters, we can recreate similar effect even on a bright sunny day, without getting our footage over-exposed.
When using ND filter, there is no typical GoPro settings. In fact you should decide what settings you are going to use before choosing ND filter with the right amount of intensity.
Shutter speed can be determined from the video FPS are you filming at, and and the amount of motion blur you aim to achieve.
Personally, I would set the shutter speed two times to four times of the given FPS. Two times has the most motion blur, and four times has less. E.g. for 30FPS, Shutter Speed would be 1/60 to 1/120.
Once you’ve done that, you can try ND filters with different value to give you the appropriate amount of exposure.
And finally, you can set ISO to determine your dynamic range of lighting (100 to 400, don’t exceed 400). See this post about how to set GoPro settings for more detail.
You can also set shutter speed to “Auto”, which is very convenient for sure, it also works great for indoor and outdoor lighting transitions. However if you are looking for the best consistency and the correct ratio for motion blur, you should lock shutter speed to a specific value.
What ND Filter to Get for the GoPro Session?
ND filters come in different strength, 2, 4, 8, 16, 32, 64 or even higher.
The number indicates the amount of light reduction, larger number means more reduction. You can stack an ND filter on top of another to increase the reduction, for examples:
- ND2 + ND4 = ND8
- ND4 + ND4 = ND16
- ND4 + ND8 = ND32
I prefer to use an ND8 or ND16 for sunny days, and an ND2 or ND4 for cloudy days. But of course this is a personal preference and depends heavily on the environment and lighting condition.
When I was searching for ND filters for my GoPro Hero5 Session, there weren’t many options because I am using a TPU mount. Those “add-on module” type simply won’t work. The closest solution was the simple “sticky film” type which you can apply directly on the glass. You can find them at GetFPV:
They are very handy because they stick right on the GoPro without glue or any help. If it gets dirty, you can just wash it with water and it will stick again.
But when it comes to image quality, they aren’t that great I am afraid. First of all, there are bubbles that I couldn’t completely remove, and you can see the tiny bits of refection in the video. And it can get permanent wrinkles if you roll or fold it. Lastly due to the surface curvature, the brightness can be uneven, the edges seem to be darker than the center.
I think the they are good enough if you just want to experiment.
Update (Aug 2018): Some have suggested that these are just 35% window tint.
Looking for ideas for your GoPro camera settings?
Session ND Filters Pack from Amazon
Next I am trying this ND filter pack from Amazon. It comes with a cap that sits directly on top of the session, and it allows you to slide the filter in. The pack comes with 4 filter options: ND2, ND4, ND8 and ND16: https://amzn.to/2HdZJbr
The solution works well, but there are some strange sun flare. Some people might prefer it, some might hate it. I think it’s kind of special effect and anyway this is still better than using the “stick-on” type of filter IMO.
The quality is okay, but it’s plastic not glass, so you might get scratches more easily.
To install it, I just tie a rubber band to the holes in the handles of the cap using zip ties. The rubber band will hold the cap tightly to the session.
I realize how much easier it is with the standard size GoPro, such as the Hero5 and Hero6. You can get push on ND filter lenses.