To ND filter or not to ND filter? That is the question.

[Feek]

I appreciate this is a very generic question, so I'm asking it to get an overall feeling, not a definitive answer.

I bought my drone about three years ago specifically to video an island, which I did. A friend of mine who's been flying drones for longer than I care to remember had a look and the only thing he picked up was that some parts of it were overexposed.

His exact words were:

"Get some ND filters so you can get your shutter speed down. You want it to be 1/fps or a multiple of. So, if you are shooting at 60fps you want your shutter to be at 1/60s or 1/120s. This gives enough blur between frame to give a really nice feeling of movement.
Shoot with shutter speed locked and ISO locked. You won't get variations in exposure when you transition from something darker to something light. Expose for the lightest part of your scene even if that means the dark bits are too dark. You can recover detail from shadows in post production but you can't fix blown out highlights."

This all makes perfect sense. Although I read a lot about drones and recording videos, I've only just started using mine again and have bought some ND filters. The type of footage I'm going to be shooting will pretty much always be landscape orientated so no fast action that needs a bit of motion blur.

Here's the bottom line:
With that in mind, does it make sense to use a filter so I'm slightly underexposing the footage rather than overexposing it and blowing it out?

 

[BobaFut]

Here's the bottom line:
With that in mind, does it make sense to use a filter so I'm slightly underexposing the footage rather than overexposing it and blowing it out?

Since you recognize that this is situational, I'll give you my very *general* feeling that I would tend to favor slightly overexposing video to slightly underexposing it, particularly if you're shooting LOG footage. Obviously if you clip your highlights you aren't getting those back, but IMO a slightly overexposed image that is corrected in post will look better than a slightly underexposed that is corrected, because of the noise that will be introduced into the video as you raise the brightness in post.

Also, just to break with the conventional wisdom a bit, if I'm just recording video for more recreational purposes, particularly static scenes like landscapes, I really couldn't care less about shutter speed and I think a lot of that "wisdom" is just people trying to sound knowledgeable (I say this as someone who does videography and pretty religiously shoots in 24fps for non-drone stuff, so I'm not immune from following the conventional wisdom).

 

[Feek]

Since you recognize that this is situational, I'll give you my very *general* feeling that I would tend to favor slightly overexposing video to slightly underexposing it, particularly if you're shooting LOG footage. Obviously if you clip your highlights you aren't getting those back, but IMO a slightly overexposed image that is corrected in post will look better than a slightly underexposed that is corrected, because of the noise that will be introduced into the video as you raise the brightness in post.

That makes sense and I think what I need to do is try some tests both with a filter (with the camera settings set to manual) and without a filter and with everything set to automatic to see what works best for me. It'll certainly make life easier to leave it all on automatic and not worry about which filter to use.

Going back some years, I used to shoot a lot of still photography with an SLR and I'd never have a lens without a skylight filter but I don't think that's quite so necessary with a digital camera.

 

[Gazwas]

Getting the exposure wrong is just getting it wrong, regardless of if you had an ND attached or not. Using an ND won't fix that and you can still overexpose with an ND attached.

The only way an ND will help expose correctly is if you lock everything in manually (ISO, Shutter, Aperture) and use the appropriate ND to balance the exposure for your chosen settings.

For landscape, with big open vistas I see very little reason to use ND as there is no real motion to blur in the footage and can soo no benefit over just leaving everything in AUTO.

The only time you might benefit from using the ND to use slower shutter speed is for top down shots when motion is exaggerated like flying over rocks, waves, treetops, ploughed fields, vineyards etc. Using a slow shutter (sometimes even slower that half the frame rate) just makes those kind of shots so much more comfortable to watch and easier on the eye when blurred.

 

[MS Coast]

The only time you might benefit from using the ND to use slower shutter speed is for top down shots when motion is exaggerated like flying over rocks, waves, treetops, ploughed fields, vineyards etc. Using a slow shutter (sometimes even slower that half the frame rate) just makes those kind of shots so much more comfortable to watch and easier on the eye when blurred.

That would be significant at lower altitude, right? From three or four hundred feet, the relative motion decreases substantially.

 

[GregS]

I'm going to experiment with filters. Starting with UV, ND8...up to ND64. Will try to video the same scene and close to the same time and see the results. I know many use an editing program and change colors, tint, contrast, etc, but I don't. I want the natural outcome, the way I saw it initially.
With the cost of these drones, and the great cameras they have, we shouldn't need to alter the results.

 

[Ridgeback65]

I agree with pretty much all the above. As a photographer who then got in to video, yes typically the ND is used to allow you to get that 180 degree shutter angle (24 fps/1/48 shutter) for “natural” video motion blur more akin to how the human eye perceives it. I have no qualms using the ND for drone with 2 exceptions. Even quality ND’s can introduce a color cast to the image. Usually this can be corrected but it’s more work in post. 2nd, if you are shooting stills and video on the same mission, you really don’t want 1/48th of a second shutter speed for stills as you risk undesirable motion blur in this case. So if you fly with an ND64 for example for “better” video shutter, the stills might be compromised and vise versa without the ND. On those occasions when I need both stills AND video, I opt for no ND. YMMV. Testing is a great idea to see for yourself!

 

[GregS]

I noticed the higher the ND filter number is, the darker the video is. I always video in Auto and I know I can change that with Manual settings, but I want to fly, not fool with settings. Will see how the testing goes.

 

[Meta4]

I noticed the higher the ND filter number is, the darker the video is. I always video in Auto

With auto exposure, the camera's metering should be compensating for the darker filter.
The video shouldn't look any darker regardless of the density of the ND filter.

 

[Feek]

I noticed the higher the ND filter number is, the darker the video is. I always video in Auto and I know I can change that with Manual settings, but I want to fly, not fool with settings. Will see how the testing goes.

I saw a video on YouTube a couple of days ago where someone shot the same scene with three different filters and the end results were almost identical because the camera settings were on auto. It effectively compensated for each filter.

 

[Ridgeback65]

Think of the ND filter as just a tool to A) help you achieve the 180 degree shutter angle for video OR B) if the light is SO bright even for stills that you need ND to get proper exposure.

Regarding AUTO settings, I highly encourage you to use manual settings--especially for auto white balance in video. As you circle around a subject, you may see the WB literally change / adapt before your eyes in the same take with auto WB. Even from take to take when you go to edit and many of the shots are different WB. Amateur look. Auto exposure is a slightly different matter where in some cases it *might help you, like if you are in a hurry, but most often not IMHO.

 

[GregS]

With auto exposure, the camera's metering should be compensating for the darker filter.
The video shouldn't look any darker regardless of the density of the ND filter.

That's what I thought would happen, but sure looks darker to me. Maybe I need to have my eyes checked?

 

[Gazwas]

The clue is in the title of the filter - Neutral Density.

ND’s will always change the colour of the shot very slightly as they only block visible light and not other wavelengths like IR. All the invisible light still streams through and hits the sensor potentially effecting colour (especially as the ND gets stronger) and even expensive IRND cinema filters still allow some invisible light through.

Colour casts are minor though and I’d never choose to us an ND to introduce a look/colour.

On fixed aperture drones, ND is for exposure control only and using one when in AUTO sort of defeats the object as you’re clueless to the settings the drone uses.

 

[Gazwas]

That's what I thought would happen, but sure looks darker to me. Maybe I need to have my eyes checked?

If you reached the limits of your iso/shutter with a strong ND filter it would eventually darken the image.

 

[slup]

...I know many use an editing program and change colors, tint, contrast, etc, but I don't. I want the natural outcome, the way I saw it initially. With the cost of these drones, and the great cameras they have, we shouldn't need to alter the results.

When it comes to auto settings, it's also a edit... but done by some Chinese engineer that decided how the metering system should react & how thing's like contrast, tint & color should look like in the final pic. So that's not technically about the quality of the camera.

If you don't like how the picture is reproduced (by this Chinese engineer)... you can revert to manual exposure settings to get a more suitable "real life" like exposure & work out from a raw to give you more headroom for post adjustments & add your own interpretation over how the contrast & colors actually were when you took the pic.

 

[MS Coast]

I saw a video on YouTube a couple of days ago where someone shot the same scene with three different filters and the end results were almost identical because the camera settings were on auto. It effectively compensated for each filter.

In auto mode and for reasonable conditions, you'd expect the exposure to be similar. But something has to change to compensate for the reduction in light by the ND filter - slower shutter speed, wider aperture, or higher ISO. The first two might change the non-exposure characteristics of the image. But if the drone has to use increased ISO, the image quality will definitely be degraded.

Also, anything you put between the subject and the sensor can add distortion and provide another opportunity for unwanted reflections and glare.

 

[Ridgeback65]

I think bottom line is, don’t use ND unless you HAVE to. Its main job on a drone is to achieve 180 degree shutter angle or a wide aperture (alas my A3 aperture is fixed) for video or perhaps a special effect motion blur look for stills. I have ND but don’t employ it often.

 

[BobaFut]

I'm going to experiment with filters. Starting with UV, ND8...up to ND64. Will try to video the same scene and close to the same time and see the results. I know many use an editing program and change colors, tint, contrast, etc, but I don't. I want the natural outcome, the way I saw it initially.
With the cost of these drones, and the great cameras they have, we shouldn't need to alter the results.

At no time in the history of photography has there ever been a "natural outcome" of a photo. Even going back to the first days photography was invented, the lens, the film, the film processing, paper, ink, etc...all had (or have, if you shoot film) an effect on the final product. Nowadays the lens, sensor, picture profile, rendering algorithms, compression, screen calibration, etc...all have an effect on the photo whether you edit it or not (and many of those decisions are made for you before the camera shows you the image you just took). A "straight out of the camera" photo will look different even just going from one camera or lens model to another or one brand to another. You don't need to edit photos if you don't want to, but not doing so doesn't make your photos more "natural." It just means that you trust the camera and lens company (and their software engineers) to tell you what your photo/video should look like rather than deciding for yourself.

 

[akdrone]

I noticed the higher the ND filter number is, the darker the video is. I always video in Auto and I know I can change that with Manual settings, but I want to fly, not fool with settings. Will see how the testing goes.

Something is off here. I had that discussion with a friend and had to toss my drone up without an ND, with an ND 8, 16 and 32 and left the exposure on Auto. All three were essentially exposed the same. The camera varied the shutter speed and ISO in order to do that as it should.

 

[akdrone]

That advice was good. For video the ND filter is only for low altitude flying where you want to be able to observe motion blur which typically works best with a fps of 30 and a shutter speed of 60 set manually. His exposure advice was good too. If you "blow out" the whites they can't be recovered and you'll have bright white patches with no tone in them. They are gone. If it is underexposed slightly the dark areas can be bumped up a bit and if something goes to pure black people are used to seeing black shadows and it doesn't look as odd as a white cloud that has a flat bright white look to it. Shooting LOG or LogM is super important here as is using the histogram to get an idea where your values lie. Clouds and snow are the biggest concern. A white background on a sign can look pure white and not look strange...so take care not to overexpose, shoot some form of Log and you'll be on your way.