I see a lot of posts regarding ND filters for people's drone cameras and each time I ask myself why; why are people buying ND filters for their drone cameras, risking their gimbal motors, potentially damaging their camera lens, etc. etc. for an almost imperceptible amount of additional motion blur if any at all. I have never used an ND filter on any drone that I have owned and I have worked hundreds of projects for paying customers over the years; not a single one has said my footage doesn't have the proper motion blur or asked for a reshoot or a refund because they could tell I didn't have an ND filter on my drone. Sure, if you are shooting the next Hollywood blockbuster and using hexacopters to lift $100K worth of cinema cameras into the air then an ND filter just makes sense.....but for Youtube, Instagram, Vimeo; where your video will probably most commonly be viewed at 320P on a 5" cell phone screen? It makes no sense at all to me.
I know a lot of people use ND filters with their drone cameras but in my opinion I think a lot of people use them just because they have read somewhere that they are supposed to use them based on the 180 degree shutter angle rule (i.e. shutter speed "should" be 2x the frame rate). But if you study the reasons why that rule came about you may reach the same conclusion that I did; which is that it doesn't make sense for drone footage.
The shutter angle/shutter speed rule is meant to reduce or eliminate flicker in certain scenarios such as at night under street lights. Well when you think about it how often is a drone in that situation? The rule is also meant to ensure that there is the "proper" amount of motion blur during fast camera movements; once again, how often is a drone close enough to an object for it to matter? So what about fast moving objects other than the drone.....once again, how often is the drone close enough to that object for the motion blur difference to really be noticeable? And if you still want that barely noticeable motion blur that you feel like you are missing...it takes seconds to add it from within your NLE as you are editing the video.
So if there's not much benefit to using ND filters on drones are there any downsides? Sure there are:
- Another Lens - ND filters are another lens between the camera and the scene which means its another thing that can get smudged, dirty or dusty, and can affect the incoming quality of light
- Image Degradation - Cheap ND filters can add a color cast, corner softness, chromatic aberration, and other problems to the image the camera records. Even the most expensive ND filters out there tend to add a slightly green cast.
- Gimbal Motor Burnout - This was the main reason I chose not to use ND filters years ago. Back then they were heavy and not designed for drones. People were reporting their gimbal motors burning out trying to support the additional weight of the ND filter on the front of the camera. What may feel nearly weightless to humans is still an additional load on the gimbal motor that was not accounted for in the original design of the drone's gimbal motors.
- Cost - ND filter sets for drones are not cheap, they are easy to break and to lose and offer marginal if any benefit to the actual footage. Drones have a very limited lifespan (the avg is 3yrs), so almost every accessory that you buy for one is wasted if you crash it or get a new drone.
- Setup Time - They add to the drone setup time. You have to figure out the proper ND filter based on the current ambient lighting situation and there's always the chance it could change drastically while you are in the air (i.e. the sun goes behind heavy cloud cover or you fly beneath tree cover).
- Camera Modification - If the ND filter has to replace the UV filter you are breaking the original factory sealed filter which will increase the chances of getting dirt, moisture, and other undesirables behind the lens. The better solutions slip over the UV filter....but then there's the weight problem.
So after looking at all of the pros and cons I personally just ignore the shutter angle / shutter speed rules and increase my shutter speed as needed to properly expose the scene. With a drone like the
EVO II 6K at F11 ISO 100 I can practically point it at the sun and still not be much over 1/200s.
Another thing people then frequently say is...
"but they've seen xyz's footage on YouTube and it looks like it is stuttering....if the YouTuber had ND filters and had properly followed the 180 degree shutter angle rule their footage would not have stuttered and been choppy". This is another common misconception; the shutter speed does not make the footage stutter, the typical cause of stuttering YouTube footage is due to whoever shot the footage incorrectly conforming the footage in post to the timeline framerate they intended to render to. Many times people shoot at 60FPS then try to export the timeline to 24FPS.....without properly configuring their NLE to account for the fact that 24FPS is not 50% of 60FPS which brings me to my next point which is that I don't understand why people shoot in 24FPS....but that's another topic/rant for a different day.
My simple advice to get the best footage out of these drones in bright daylight; shoot at 60FPS or 30FPS, use a 30FPS timeline (29.97FPS), render your footage at 30FPS (29.97FPS), push the F stop to F11 and keep the ISO at 100, then use whatever shutter speed is needed to properly expose the footage and leave the ND filters to the regular cameras or the Hollywood blockbusters. BTW, I have absolutely nothing against ND filters themselves, I use them nearly daily with all of my other cameras to control the shutter speed either for video or for photography; its just that when it comes to drones I can't think of a single use case where they would provide any value whatsoever.
unsplash.com
