What are ND filters? They’re often offered up as an add-on accessory for your drone. So do you need them?
If you want to level up your drone photography, then yes, ND filters are a must-have accessory in your drone kit. Especially if you use your drones to take photos during the day in bright conditions (and even if you’re filming at dawn or dusk but want to experiment with unique effects), you should know how — and likely own – a set of ND filters.
What are ND filters?
An ND filter (short for Neutral Density filter) is a tiny piece of glass (or sometimes resin) that you pop on your camera lens. Typically the ND filter is darkened, intended to reduce the amount of light entering the camera lens — all the while preserving the colors in the image. Think of them like sunglasses for your camera lens.
Neutral density filters have several important functions, including:
- Avoiding blown-out images: ND filters allow you to control the exposure of your camera in bright conditions. By reducing the amount of light entering the camera lens, you avoid overexposure, which is often common when flying drones in open spaces on bright, sunny days. No more overly-white, too-bright images.
- Allowing for motion blur: By reducing the amount of light entering the camera lens, ND filters also allow you to use slower shutter speeds to create motion blur in your images or videos, even if it’s otherwise bright out. That allows you to achieve the aesthetic of motion in your images, particularly common in shots such as waterfalls, athletes or vehicles. They’re also common for those cool, long-exposure shots at night where the landscape is still but you see light movement from something like a car.
- Reducing lens flare: ND filters can also reduce lens flare, which is caused by light reflecting off the lens. While sometimes an intentional aesthetic for dreamy-style photos, they can also create an unintended, annoying haze (sometimes referred to as ghosting) or glare in your images. ND filters can reduce the amount of light entering the lens, which can help reduce lens flare and improve the clarity of your images. With ND filters, you have sharper, more vibrat images.
- Eliminating jello: For videographers, there’s a similar reason to use ND filters: reducing “the jello effect.” This is frequently caused by vibration or movement of the drone, but can be toned down by ND filters, resulting in smoother footage.
Here’s an example of how the ND filter provides a sharper, more vibrant image:
As you shop for ND filters, there are a few things drone pilots should know:
ND filters come in different strengths
ND filters come in different strengths or densities, which refer to the amount of light they block. So for example, ND4 filters block 25% of the light, while ND16 filters block 94% of the light, and so on.
You might use a ND4 2-stop neutral density filter for filming on mild days or during the golden hour (the first and last hour of sunlight in a day). It’s also useful in reducing highlights and lens flare.
The ND8 3-Stop neutral density filter should be used on bright days to help prevent lens flare and mild rolling shutter.
The ND16 4-stop filter is one of the darker shades. It works well on very bright days and creates the smoothest cinematic look to your videos of all the filters.
Choose the right strength of ND filter based on the lighting conditions and the effect you want to achieve. Here’s a pretty useful cheat sheet, provided by the folks at ND filter leader Polar Pro:
They bring their own challenges, too
While it’s easy to sing the praises of ND filters, realize that they can also initiate new challenges that can negatively impact your drone photography. For starters, they often end up interfering with autofocus and image stabilization, especially if they are not properly installed or if they are of poor quality. Choose high-quality ones that are specifically designed for your drone camera (PolarPro products are reliably great), and follow the manufacturer’s instructions for installation and use.
You generally want to buy circular filters, as they tend to be able to quickly and seamlessly affix to your drone’s camera lens. Square filters are typically more cumbersome, as they usually require a filter holder and adapter ring.
You might find adjustable ND filters
You might stumble upon something called a variable ND filter, which means it’s adjustable so you can control the strength of the filter and the resulting exposure.
These optically-transparent filters allow you to adjust opacity and reduce brightness of the light between two to eight stops, without effecting color or anything else.
ND filters are not one-size-fits-all
The most common consumer drones commonly have filters designed specifically to fit them. It’s almost always a good idea to buy filters designed specifically for your drone, as they’re generally designed with precise snap-joints that ensure a reliable fit and lens seal during flight.
For $55, you might buy the DJI Mini 3 Series ND Filter Set, which comes with ND16/64/256 filters and are compatible with the DJI Mini 3 Pro and DJI Mini 3. Mavic 3 owners will have to fork over a heftier $129 for a filter set, which includes ND8/16/32/64 filters (hey, at least you get four instead of three). Those sets are designed and manufactured by DJI itself.
Some of the smaller drone companies outsource to other companies to take on the task of filter-making, such as PolarPro. Costa Mesa-based PolarPro makes a variety of photography accessories, but is primarily known for its ND filters. It makes filters for a range of drones (and often they’re either cheaper or better quality than buying the ones directly from DJI).
PolarPro works directly with other companies to provide their matching filters, as is the case with Skydio. PolarPro offers a $70 kit of ND8, ND16, and ND32 filters that were engineered specifically for the Skydio 2/2+, and they affix via a seamless magnetic connection.
Don’t overlook the value of neutral density filters
ND filters can be one of the most underrated ways to level up your drone photography. They’re almost always an additional expense on top of an already-expensive drone.
And a lot of drone photographers fall prey to the false assumption that software can fix everything. While post-processing software can fix some issues with exposure, it cannot compensate for overexposure or underexposure to the same degree that ND filters can. Additionally, software cannot create motion blur or reduce lens flare in the same way that ND filters can.
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