ND filters are common filters to have while shooting video with any camera, but if you don't want to have multiple filters with varying strengths and swap filters - there are a number of Variable Neutral Density filters out there to choose from.
Breaking variable neutral density filters up into two different strengths from 2-5 and 6-9 makes them easier to use by limiting the amount you can turn adjust the filter. If you had a 2-9 stop filter, you would easily have spots of darker areas of cross-polarization in your image. This happens when the two polarized lenses move too far on the lens and give you some poor results. That's not to say the cross-polarization is completely eliminated with these filters, but it is less likely. Anytime you have a variable ND, there will be two polarizing filters moving relative to each other, this is what makes your image darker or lighter depending on which way you turn the front element on the filter.
Freewell advertises these are waterproof and scratch proof, I haven't tested this very vigorously, but I have touched the outside edge of this filter multiple times while adjusting it and I haven't had any scratches on it yet. It's helpful to know whenever you'll have to adjust the lens, it won't scratch easily. This filter being so small, it's inevitable that you'll touch the front of this filter while adjusting the filter strength.
When I first saw variable ND's for the Mavic Air 2, I was curious to see if the drone's gimbal could be turned off and on, as well as attach the gimbal guard to the drone without taking off the filter. The filter is slightly larger than other ND or filters, it's similar in size to an ND/PL filter. After some testing, I'm happy to find that I'm able to turn the drone on and off with this filter attached, as well as being able to put the gimbal guard back on.
A great part about Variable ND filters vs traditional ND filters, is you have the ability to adjust the strength to half or quarter stops if you really want to. If an ND 16 is too strong, while an ND 8 isn't aggressive enough, with a variable ND, you can dial in somewhere in between those two amounts.
With all that turning though, try not to touch the front element of the filter or you can smudge the edges of your filter and have blurry footage because of it. Again, this is an inevitable part of using a variable neutral density filter with such a small camera, so be sure to check your lens for smudges before take-off and have lens wipes with you while using this lens.
The beauty of Variable NDs is you can usually get away with just using the 2-5 stop ND filter. Unless you're filming in very bright situations or long exposure photography, you'll likely use the 2-5 stop for most of the time. This means that if you're filming at golden hour, and the sun starts to rise more in the sky, you can adjust your vnd without needing to remove your filter. You can simply move the indicator from 3 to 4 to move from ND 8 to your ND 16.
This also cuts down the need for multiple filter sets, so you won't have to take as many filters along with you. Again, that comes with the trade-off of needing to pay attention to not get those cross-polarization patterns in your shots and not smudge your lens while adjusting it.
In my experience with this filter, the 3-5 settings had some cross-polarization happening. The 3 wasn't that bad, going up to 5 made it worse. It was a little more subtle while flying around, but to better illustrate this, I pointed my Mavic Air 2 towards my whiteboard to show this a little better. With the 2-5 stop ND, setting 2 has no dark spots, while 3 had light cross-polarization on the top left and bottom right, while the 4 and 5 settings had the cross-polarization is more pronounced. The 6-9 filter had slight cross-polarization at stronger strengths as well, but it wasn't as bad as the 4 and 5 settings on the 2-5.
This is something to keep in mind if you film with an ND 16 or ND 32 frequently. For when I use which filter, check out my ND filters video - I'll leave that link in the description.
I hope Freewell addresses this in the future and makes maybe a 1-3, a 3-6, and a 6-9 VND - as this would probably remedy the cross-polarization all together. There will be more filters, and it would be "less convenient" than just 2 filters but the overall quality of the filters would be better.
The Freewell filter also makes the overall image warmer and darker, so I made a D-Cinelike to "normal, natural" colors LUT to apply in post to easily color grade this footage. I made more LUTs for IR cut and Clear Night Freewell filters as well as some other filters and no filter. If you're interested in my D-Cinelike to natural LUTs, there will be a link in the description.
Some other things to note, after adjusting this lens and getting a smudge on it, I wiped off my filter not being very careful and I got a gimbal overload error after taking off. So be careful when cleaning your lens while it's on the drone and powered on.
For some people, a variable ND filter is the only filter they will need, while others may want to have multiple filter sets for different shooting environments. I like VNDs for quick shots, where I don't want to shuffle around multiple filters, but be careful of that cross-polarization that could happen in certain situations.
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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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