Best ND filters for GoPro
GoPro cameras are still used for many drone filming applications. For example, I use GoPro cameras with some of my FPV drones.
To get the best footage from GoPro cameras, you will need to ditch the Auto feature and delve into settings like frame rate and shutter speed. This is how stunning cinematic motion blur can be achieved with GoPro footage.
However, there is a (not very secret) tool that you will need for this to work well and that tool is neutral density (ND) filters.
What are ND Filters?
ND (neutral density) filters are like sunglasses for a camera. They allow for longer exposures without over-exposing the camera sensor.
To manage exposure without an ND filter, the shutter speed can be increased or made faster.
However, to maintain correct exposure in bright conditions the shutter speed may be so fast that footage from the camera becomes choppy because each frame is not exposed for long enough.
Choppy footage is particularly noticeable when objects in the footage are moving.
Therefore, slowing the shutter speed and using an ND filter helps maintain correct exposure and make the motion in the footage look smooth.
However, lowering the shutter speed by a lot can introduce significant motion blur in the footage.
The 180-Degree Rule
So how do we choose a shutter speed suitable for the frame rate and subject that we are filming with? There is a useful term in videography and cinematography known as shutter angle.
Shutter angle comes from capturing footage on film, with film cameras having a shutter that rotates to expose each frame.
The angle between openings on the shutter determines how long the film is exposed for.
Typically, for natural motion blur, a 180-degree shutter angle is used. This equates to the shutter speed being twice the frame rate.
For example, if filming at 24 frames per second, then at a 180-degree shutter angle, the shutter speed would be 1/48s.
180-degree and 90-degree shutter angles work well with GoPro cameras, with a 90-degree shutter angle being twice as fast a shutter speed than a 180-degree shutter angle.
For example, shutter speed is 1/96s at 24 frames per second for a 90-degree shutter angle.
However, at lower frame rates, even a 180-degree shutter angle can introduce too much motion blur when filming fast motion.
ND Filter Range
ND filters are typically tinted glass and are usually sold in sets with various tints to suit a variety of conditions. Increased tint corresponds to a higher ND filter value.
Deciding which tint or filter value is suitable for correct exposure can take a bit of trial and error, but becomes easier with experience.
For reference, on a bright day, ND16 or ND32 filters give good results with GoPro cameras, however, this will vary depending on the frame rate and shutter angle selected.
GoPro Specific ND Filters
There is also a range of different types of ND filters available for GoPro cameras. There are ND filters that simply slide over the stock lens of a GoPro with a friction fit.
These are a cheap option to start using with your GoPro and are thus cheap to replace if they become damaged. However, a friction fit isn’t the most secure option and the ND filter could be knocked off.
There are also magnetic ND filters available. These are generally made for the Hero 8 camera. These claim to provide a more secure mounting than friction-fit ND filters, at a slightly higher cost.
There is an optional type of ND filter that can be used in place of the foremost lens on GoPro Hero 9, 10, and 11 cameras.
The foremost lens of these GoPro cameras can twist off and on. These are known as twist-on ND filters. For example, GoPro sells Polar Pro ND filters with this twist-on mounting system.
ND filters from other brands such as Freewell, Telesin, Skyreat, and Camera Butter are also available. See below:
02/22/2023 01:03 am GMT
This is probably the most secure mounting option for ND filters but does mean the innermost lens of the GoPro is arguably less protected in comparison to using a friction fit or magnetic ND filter over the stock outer lens.
Choosing the Best ND Filter Type for your Needs
So which type of ND filter is best?
Considering that the force needed to dislodge a friction-fit mount ND filter off a GoPro is quite reasonable, a friction-fit ND filter set will work well for most people.
I use friction-fit ND filters on a GoPro on my FPV drones as well as on my helmet for mountain biking and motorcycling. I am yet to lose a friction ND filter in any of those scenarios.
Given that the availability and cost of some twist-on ND filters for newer GoPro cameras are comparable to friction-fit filters, twist-on ND filters are probably the best type of ND filter to use with a GoPro.
There is also less risk of twist-on ND filters vibrating and causing problems with footage when compared to friction fit or magnetic ND filters.
It is worth shopping around for twist-on ND filters. You could save some cash compared to buying Polar Pro filters direct from GoPro.