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// Tutorial / How To

How do ND filters work and how will they affect my DJI Mavic footage?


Many DJI Mavic pilots use neutral density (ND) filters to capture the best quality content in camera.  Doing so means that they aren’t stuck editing over exposed, choppy footage that looks more like cheap action cam footage than quality droneography.   If footage is over exposed, it won’t be possible to reduce highlights and other noise.  That’s a bummer when you’ve just recorded epic 4K content with your DJI Mavic Pro, Pro Platinum or new Mavic Air.  But with the right ND filter, you can capture smooth, cinematic content that requires little to no post processing.    


How do Neutral Density Filters work


ND filters reduce the amount of light that reaches a camera’s image sensor.  By reducing light, neutral density filters sort of ‘trick’ the camera into using a slower shutter speed.  This slower shutter speed creates smoother looking video, useful when filming in bright daylight with the Mavic’s shallow depth of field.  ND filters are important in capturing properly exposed footage with the DJI Mavic platform since both the Pro and Air have fixed apertures.  Because of their shallow, fixed apertures, the Mavic Pro and Air both struggle to maintain correct exposure in bright light.


What do ND Filters do?


PolarPro, who designs filters and drone accessories, has been producing top notch filters for the DJI Mavic platform since the first Mavic model came out in 2016.  PolarPro offers ND filters that provide control over shutter speed without shifting the camera’s color profile.  PolarPro also offers hybrid neutral density/polarizing filters.  ND/PL filters provide enhanced color saturation and glare reduction when flying over water, snow, or desert sand.  These hybrid ND/PL filters also help reduce glare and improve color saturation when flying over bright, reflective cityscapes. 

So, we know that ND filters reduce the amount of light that reaches the camera sensor.  We know this will slow down shutter speed to produce smoother video in bright daylight conditions faced by UAV pilots.  But how does a slower shutter speed correlate to smooth video?  It’s got everything to do with the ratio of shutter speed to frame rate.

In cinema, there’s an industry standard that states that a camera firing at a shutter speed twice as fast as its frame rate will produce the most natural looking video.  Cinematographer’s from the days of film found that a shutter angle of 180 degrees is the rate at which each frame blends together to produce the most natural movement frame to frame.  This rule is often referred to as the 180 Degree Shutter Rule, and it’s important for videographers to know.  In today’s digital terms, a 2:1 shutter speed to frame rate ratio is the equivalent of using a 180 degree shutter angle.  In photography, you can choose from multiple shutter speeds.  In cinematography, however, you’re either shooting 24 or 25 frames per second (FPS), and your shutter speed is tied to that value, as well as to ISO.

When shooting in Manual mode, ND filters allow you to change your Mavic’s exposure settings. This includes ISO, and most important for all DJI Mavic pilots, shutter speed.  Let’s say you’re shooting with the Mavic Pro or Mavic Air on a sunny, cloudless afternoon, at 4K/30 FPS with ISO at 100 to limit noise.  With a current shutter speed reading of 1/1000th, your footage is going to come out choppy with that fast action cam look.  Increase shutter speed under these conditions and you’re left with bright, washed out footage that looks white.  If you increase ISO, you’ll just get more noise.  To achieve a smooth, cinematic look, you’ll need to use the right ND filter to reduce your shutter speed to near 1/60th without changing your other exposure variables.  The right ND filter on your Mavic camera will allow you to keep ISO low while maintaining control over shutter speed.  For this scenario, a 4 stop (ND16) filter would reduce your shutter speed to 1/60th.  The end result?  A smooth, balanced exposure fit for the big screen. 


Hoe do ND filters change video


Because of the limited dynamic range in both the DJI Mavic Pro and Mavic Air models, ND filters are also useful in helping to match Mavic footage to content captured with full sensor, production grade cameras that have larger, more capable dynamic ranges.  One advantage that the Mavic Air has over the Mavic Pro is a slightly smaller aperture.   The Mavic Pro has an f/2.2 aperture lens while the Mavic Air has an f/2.8 aperture lens.  This is a difference of about 2/3 f stops of light.  This small difference, however, makes it easier to capture shots that are in critical focus.  However, with the same limited dynamic range as the Mavic Pro or Pro Platinum, the Mavic Air can still use all the help it can get.  ND filters are by far the simplest fix to consistently correct washed out footage.

Because most UAV content is filmed during daylight hours,  neutral density filters become essential to capture correctly exposed video.  Whether you have the Mavic Pro, Pro Platinum or DJI’s new Mavic Air, ND filters will allow you to lower shutter speed and limit ISO when filming with a fixed aperture in bright light.  Whether you need a ND4 for filming at dusk or dawn on the coast, or ND64/PL for extreme desert sun at 24p, PolarPro makes quality ND and ND/PL filters that will help you capture perfection in any setting.


What do Neutral Density filters do

Tutorial / How To

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