A common question I get asked is "do you need nd filters for video", and if so what strength ND filters - and even further, should I get ND filters with polarization?
ND filters do matter if you're trying to shoot cinematic video in bright environments. When it comes to polarization, that can depend on your shot.
First off, let’s get a better idea of what ND filters do, and what polarizing filters do for your camera.
ND filters are designed to reduce the amount of light that reaches your camera's sensor. If your exposure is too bright, shooting with ND filters will help bring the exposure down to a normal level without adjusting your camera settings. This is common for filming in bring environments while shooting at a 180-degree shutter angle, meaning your shutter speed is double your frame rate. For the examples in this video, I was filming at 24 frames per second, so my shutter speed was 1/50th. This achieves natural-looking motion blur on moving objects that are aesthetically pleasing to your eye and doesn’t look “digital”, or too blurry. However, during the day, with my aperture at a fixed 2.8 and my ISO at 100, my shot was very overexposed. This is where ND filters help.
Another common question is do you need nd filters for photography? And again, it depends on what you want to do. Shooting with a slow shutter during the day could allow for a lot of motion blur in moving subjects, but this will also increase your exposure. At night, you may need to use a slower shutter to properly expose your shot, and an ND filter would make your shot underexposed here. Using the correct strength of the ND filter for your application will decrease your exposure to normal levels while maintaining your desired shutter speed. Shooting landscapes with a slower shutter and an ND filter is common in photography, but hard to do with a drone, since wind and the vibrations of hovering move the drone slightly, making for a blurry image. It can be done with a drone, but it's difficult.
Polarizer filters are designed to remove the glare and reflections from objects in your shot. If you’re filming reflective surfaces like cars, glass buildings or water, it’s good to use a polarizing filter. Cutting down glare will add more detail to your shot, where the glare was previously. Removing the glare will also bring your overall exposure down, one thing to keep in mind with polarizing filters though, is that they must be adjusted to get the proper polarization to remove the glare and reflected light.
It can be tricky to get the proper alignment but were going to be using polar pro's Vivid collection which has an advertised "polarization indicator" that was going to test to see if it makes it easier to judge the polarization. This is especially handy if you're using a drone because if you get the polarization wrong, you're going to have to bring the drone back, land, and re-adjust the polarization on the lens.
I went to my go-to testing spot in the middle of the day for maximum glare off of the water. In this test, I flew without a lens to simulate what a proper 180 shutter angle would look like without a filter, and I took the ND16 from DJI that comes in the Fly More kit and a polarized ND16 PL from polar pro's vivid collection line of filters.
The first test shots were orbiting the pier, and all of these shots may look a little muddy or washed out at first because I shot them in D-Cinelike on the Mavic Air 2.
Each of the filters has slightly and I mean really slightly different color casts from the stock no filter, but to make my editing life as easy as possible I made some corrective LUTs with my Color Checker passport in DaVinci resolve. If you're interested in my D-Cinelike to 'neutral' LUT's for no filter, the DJI filter, and the Polar Pro filter that I'm using in the video, check out the link in the description.
For camera settings, were staying with the 180-degree shutter rule at 24 frames per second. ISO 100 and a fixed 2.8 aperture.
First up, no filter. This is obviously really overexposed and needs so major help.
That is where the ND 16 from DJI comes to bring down the exposure of our shot. The ND helps bring the exposure of our shot down without adjusting our camera settings. You can see in the edges of the frame where the pier is moving quickly, there is some gentle motion blur that our slower shutter speed is allowing us to capture. This blur is more obvious with faster moving subjects, but for the sake of this test - that's the most motion blur we're going to get here.
Next up is the Polarized ND16 filter from Polar Pro. This filter is following Polar Pro's best practices were filming with the line on the filter at 12 o'clock at the top of the filter. This seems to hold true and have a polarizing effect on our footage. The ND16 is keeping our exposure low, just as the DJI filter was, but in addition to cutting down light that's hitting our camera, this filter is also removing some of the glare off of the water as well. You can tell the difference in reflections when comparing the ND16 PL to the ND16 side by side.
After flying the Polar Pro filter at the 12 o'clock, I decided to adjust the filter to 6'oclock and see how this affected our image. Overall, the image looks pretty similar. Maybe not as strong as 12 o'clock.
After that flight, I wanted to find a spot where the filter didn't perform as well - just to make sure I'm getting the best performance out of this lens. So I decided to then put it in the 9 o'clock position and see how this worked. And as suspected, the polarization didn't work as well - and the overall image was brighter due to the lack of polarization. This filter performed more like the DJI ND16, maybe a little bit weaker.
One thing to mention here though is that the polarizing filter will remove most indirect glare, but it won't remove all of the glare. There is still some glare coming off of the water when the sun is directly reflecting off of the water and onto this lens. So even if you're using a polarizing lens, and it's aligned properly, there will still be some direct glare or reflections affecting your image. The polarizer cuts out a large majority of the reflections, but not all of them.
This is most apparent when were looking at the water, straight down from the top of the pier. While the polarizer did a good job at removing the indirect reflections coming off of the water, the direct reflections from the sun are almost the same on all of these filters, even the polarized filters.
If you're going to be shooting cinematic video in the middle of the day, or at any time of day, you're probably going to need an ND filter. Where the filters get interesting is when we add the polarizing filters into the mix. If we have some indirect reflective surfaces, the polarizer can cut out the light reflecting from those surfaces, only if it's properly aligned. And if it's not aligned, it could work about the same as a regular ND filter, but you can experience some weird cross patterns or dark spots from the polarization if you're not careful.
If you do not need to cut out reflections, regular old ND filters are going to be the easiest to use. If you need to cut down those reflections in your shots, just make sure to have your polarizer properly aligned, I like that the Polar Pro filters have the alignment markers as well.
Another common question I get asked is what strength of ND filters do you recommend for what times? I'll give you my brief overview of how I choose ND filters when shooting at 24 frames per second. Just a disclaimer, this is an oversimplification, and I live in Ohio, so if you live in a brighter area, maybe go up a strength. Oversimplification, but here we go.
I use an ND4 at golden hour when it's overcast, an ND8 at golden hour when it's clear, ND16 for the middle of the day in semi-cloudy conditions, as the example footage in this video, ND32 for blazing hot, bright days with no clouds, I've only used an ND64 a few times and it was super bright in locations closer to the equator.
If I had to choose only 3 filters, I'd go with an 8, 16, and 32. Those are the filters I use the most when shooting cinematic video at 24 frames per second. I was recently in California for a week driving the pacific coast highway from San Francisco to San Diego, and didn't use anything over an ND32.
Hopefully, that helps when it comes time to choose between no filter, an ND filter, and a polarizing ND filter.
I'm a designer from Cleveland, Ohio and love to shoot photos & videos. I made my first website in 2004 to show friends photos & videos (before YouTube/Flickr were things) and have been shooting and designing ever since! I have a deep passion for making and helping others create.
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