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OK, What's the deal with ND Filters? (Or "Has the world gone crazy?")

Wombat55

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New Mavic owner here but long-time amateur photographer. I have to say that I'm really puzzled about the current craze about using ND (neutral density) filters with drones like the Mavic. OK, so the Mavic's camera has a relatively fast f/2.2 lens with a fixed aperture. Possible over-exposure problems with too much light, but I've been flying the Mavic here in sunny California without an ND filter and without noticing any apparent overexposure problems in the pictures or videos. Last time I was flying around noon on a sunny day, and glanced at the shutter speed on my control. It said about 1/1000 shutter speed, which is fine. That certainly wouldn't make me reach for an ND filter if I were shooting my DSLR with the aperture wide open. And if I don't need an ND filter when flying on a sunny California day, when would I possibly need an ND filter?

Curious, I looked on Youtube and on the internet for some examples about the supposed superiority of Mavic pictures taken with ND filters but had a hard time finding any convincing evidence for using such filters. One example of with- and without-filters showed two pictures side by side with the "without-filter" picture clearly being out-of-focus, which of course has nothing to do with having or not having filters. Another example showed two pictures of a bay with some fine water ripples being evident in the picture taken with an ND filter but none in the picture taken without the filter. The problem is that I wasn't convinced that the reason for the difference wasn't really because a slight breeze hadn't picked up between the "with filter" and "without filter" drones flights. In fact, I'm pretty sure that that was the reason for the difference. Finally, another example shows picture shots of an ocean looking directly into a setting sun which, admittedly, is a condition where one might expect to see the most improvement with using an ND filter. However, even there the improvement was, in my opinion, modest. Sure, a little bit more of the reflecting water surface was saved from overexposure, but even an ND16 filter isn't going to completely eliminate overexposure if one is looking directly into the sun.

So my opinion at present is that the whole issue of using ND filters with the Mavic and other drones to get better images may be a little bit overhyped. With rare exceptions such as taking pictures in an area covered by snow or for pictures almost directly into the sun, ND filters (IMHO) are really not needed. I certainly don't have any plans to buy any ND filters for my drone. (And, in fact, with the exception of "specialty shots" such as rare occasions when I want to slow down the shutter speed without decreasing the aperture or ISO for shots of, say, a waterfall, I hardly ever touch my DSLR ND filters, either. I only got my DSLR ND filters many years ago when I was new to photography because of a naive belief that "real" photographers were supposed to have a full set of ND filters.)
 
That's with the basis of photography, which ND helps to reduce shutter speed from getting overexposed photos.

Things work differently for videos, NDs are used to avoid having excessively high shutter speeds as that would make video captures "less smooth". Photography is made with just a single frame so whatever parameters you dial in only affects a single frame/photo; videos are pretty much a long chain of frame captures and rule of thumb is to get shutter speeds 2x of your frame rate.

If you are getting NDs purely for drone photography then personally I say that's unnecessary.
 
For us still photogs the idea that every frame should have a little movement for smooth video takes a little to wrap our brains around but you will likely wanna shoot video at a shutter speed 1/50th or 1/60th for or else you get jittery looking results with moving subjects.


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I think a lot of hobbyists kind of get a "cargo cult" personality, where they hear their friends raving about some accessory, and whether they understand the actual finer points of that accessory, they go buy one. So many videos parrot the same misunderstandings of what ND filters do, and can do, and can't do, that it's pretty funny really.

If you take two photographs of a calm scene, one with a super-dark ND filter and one with no filter at all, you probably won't notice any difference at all right away. The camera compensates for the darkness so everything ends up the same brightness anyway. The crisp or deep focus is the same. The contrast is the same. The hue is the same. The saturation is the same. None of that changes. What might give it away is if there is anything moving quickly in the scene. An ND filter will add more motion blur. Still images are unchanged. That's the whole point of the "neutral" in the name. (An ND filter will also reduce high-speed sensor sensitivity noise by dint of selecting a lower ISO value, but since you probably won't use such filters on drones in dark situations this is irrelevant.)

It isn't all bad, though... lots of photogs are now learning about the benefits of motion blur in videography.
 
OK, I'm starting to understand. But if what you guys are saying is true and that the advantage of using ND filters really isn't in improving still pictures or nearly static video scenes, but improving the smoothness of video which is panning a scene or showing a moving object, then it appears that there are a LOT of people who really don't understand the whole point of ND filters on drones because I came across a lot of examples of attempts to show the supposed superiority of ND filters by people who simply showed a single video frame or a video of some static, still scenery!
 
New Mavic owner here but long-time amateur photographer. I have to say that I'm really puzzled about the current craze about using ND (neutral density) filters with drones like the Mavic. OK, so the Mavic's camera has a relatively fast f/2.2 lens with a fixed aperture. Possible over-exposure problems with too much light, but I've been flying the Mavic here in sunny California without an ND filter and without noticing any apparent overexposure problems in the pictures or videos. Last time I was flying around noon on a sunny day, and glanced at the shutter speed on my control. It said about 1/1000 shutter speed, which is fine. That certainly wouldn't make me reach for an ND filter if I were shooting my DSLR with the aperture wide open. And if I don't need an ND filter when flying on a sunny California day, when would I possibly need an ND filter?

Curious, I looked on Youtube and on the internet for some examples about the supposed superiority of Mavic pictures taken with ND filters but had a hard time finding any convincing evidence for using such filters. One example of with- and without-filters showed two pictures side by side with the "without-filter" picture clearly being out-of-focus, which of course has nothing to do with having or not having filters. Another example showed two pictures of a bay with some fine water ripples being evident in the picture taken with an ND filter but none in the picture taken without the filter. The problem is that I wasn't convinced that the reason for the difference wasn't really because a slight breeze hadn't picked up between the "with filter" and "without filter" drones flights. In fact, I'm pretty sure that that was the reason for the difference. Finally, another example shows picture shots of an ocean looking directly into a setting sun which, admittedly, is a condition where one might expect to see the most improvement with using an ND filter. However, even there the improvement was, in my opinion, modest. Sure, a little bit more of the reflecting water surface was saved from overexposure, but even an ND16 filter isn't going to completely eliminate overexposure if one is looking directly into the sun.

So my opinion at present is that the whole issue of using ND filters with the Mavic and other drones to get better images may be a little bit overhyped. With rare exceptions such as taking pictures in an area covered by snow or for pictures almost directly into the sun, ND filters (IMHO) are really not needed. I certainly don't have any plans to buy any ND filters for my drone. (And, in fact, with the exception of "specialty shots" such as rare occasions when I want to slow down the shutter speed without decreasing the aperture or ISO for shots of, say, a waterfall, I hardly ever touch my DSLR ND filters, either. I only got my DSLR ND filters many years ago when I was new to photography because of a naive belief that "real" photographers were supposed to have a full set of ND filters.)

I stated yesterday that if you ran a survey asking which video hobbyists preferred of a video with & without filters (without revealing which video used a filter) then the results would be pretty close. Most hobbyists would be better off just spending the money on a sun shade.
 
I most hobbyists would be better off just spending the money on a sun shade.

What is a sun shade?

I'm a professional photographer of over 20 years and videographer for 5 and I always get a good laugh at all the nearly useless doodads, adapters, and seemingly magic tricks that get promoted on photo forums when the laws of physics and the mechanics of capturing imagery changes little.

For example the Sunny 16 rule applies here which states that on a bright sunny day you exposure should be pretty darn close to 1/ISO at an aperture (or iris) of f16. That means if you're shooting at f16 and the lowest ISO of 100 then your shutter speed will be 1/100.

Since our target shutter speed for smooth video shot at 30fps is 1/60 we need to reduce the light entering the lens. We can do that by either lowering the ISO (sensitivity), using a smaller aperture like f22 or adding a ND filter to the front to cut the light in half. If our lens doesn't have an f22 or our ISO doesn't go lower than 50, the ND filter is out only option.
Or, we can wait for an overcast day or try to avoid much movement and hope that our audience doesn't notice.

True story, I have some video footage I shot in HDV from a helicopter of barges going down the river before I understood all of this years ago. Shutter speed was likely 1/125th. The boat wakes jiggle and dance and drive me nuts. But, I've licensed that footage for real money to advertising and corporate clients multiple times over the years. Moral of the story is content matters far beyond technique and you only have to please the intended viewer.

Another reason you might want an ND filter is to allow you to shoot at a much larger aperture on a larger format lens like a DSLR or Super35 and get a shallow depth of field to blur the background. That is not much of a consideration on these small sensor wide lens cameras though.

ND filters are not magic, they are just one more tool in the arsenal. If you're shooting video in bright light, you're probably gonna want one but learn when you need it and when you don't.




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Same purpose as a DSLR's sun shade: incident light falling on the lens is caught by dust or surface imperfections on the lens and creates glare that reduces contrast.

Ah, what I'd call a hood and I didn't know they made them for drones. Thanks now I must have one!

Reminds me of the downside of adding an additional piece of glass to the front of any lens is that it increases the risk of glare or refractions that can have the same effect. That why I say, only use the filter when needed.


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Hey, another thought about this whole issue of using ND filters to slow the shutter speed while taking video clips so that the videos show "natural" motion blur: As we all know, Photoshop has pretty much made the use of many types of color filters obsolete. No need for a color filter if you can take pictures without a color filter and then post-process with Photoshop to achieve the same effect as a color filter, right? Now what about the issue of using ND filters to introduce "natural" motion blue of any moving objects in a video clip? It occurs to me that, just in the case of color filters, it shouldn't be too difficult for a computer application to mimic the effect of an ND filter in regards to blurring the features of moving objects. The computer program would look for regions of the picture frame in which pixels are rapidly changing value and apply some algorithm to introduce some motion blurring of those regions.

OK, I'm describing the procedure in very broad strokes here and certainly there would probably be a lot of details to work out in terms of fine-tuning the algorithm. But the fact remains that with the computing horsepower available to modern day personal computers and the great amount of work that has been done in the field of practical image processing by programs such as Photoshop, I can't believe that it should be that difficult to achieve the same motion blur effects as an ND filter by using proper post-processing of a video clip taken without an ND filter. Just as in the case of color filters, an ND filter isn't doing anything that can't be done by an appropriate computer algorithm,
 
Just as in the case of color filters, an ND filter isn't doing anything that can't be done by an appropriate computer algorithm,

While I'm sure this is true theoretically, keep in mind that we're talking about 24-60 frames per second. Not to mention having to come up with an algorithm that blurs the pixel in the direction of the movement. That's a lot of frames to analyze and entirely unnecessary if done right "in camera." Much easier to put a filter on unless you just like to spend time behind a computer screen.

I occasionally use software to correct color balance or even to stabilize video, but I always kick myself for having been too lazy to get it right in camera. I'd rather be shooting.


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Fly it a little more and you'll realize it's utterly useless without ND filters in extremely bright scenes, in the cold, in the wind, or, in the case of most of my shooting, all three. It has nothing to do with correcting exposure and everything to do with getting the magical, slower shutter speeds. Above 1/120th and below 55F or in any kind of wind, this thing is jello city.
 
Firstly, Im new to video but still photography I am good with and have had my Mavic less than a week.

My understanding is to get smooth pans and movement clips you want your shutter speed no faster than twice your frame rate. On a sunny days this is a problem.

Firstly the Mavic has a fixed aperture of f2.2. And secondly the Mavic's lowest ISO is 100.

Sunny f16 rule says exposure should be: ISO 100 shutter speed 1/125 and aperture of f16.

If we set the video frame rate to 30 fps, 1/125th is still too fast a shutter speed.

Change the shutter speed to 1/60th means the frame rate is OK but the exposure is one stop over. ISO 100 . f16 . 1/60th = +1EV

To correct the exposure we need to change aperture to f22

As the Mavic does not have f22. introduce ND filters to reduce required aperture to f2.2.

The difference between f 22 and f2.2 is about 6 1/2 stops. ( lets call it 6 stops )

A six stop ND filter is ND 64 ..... And if you want to get that 1/2 back into the equation, you should use an ND128.

Now I think something is amiss here because I have not seen many ND 64's let alone ND 128's.
 
Remember how f-stop is calculated. Aperture of f/22 is suitable for full-frame 35mm camera geometry. Aperture 2.2 is common for 8 gram micro cameras like cellphones. Any smaller and you would be getting edge diffraction artifacts.

Also there is no fixed definition for numbering neutral density filters. One company's ND8 can be another company's ND256 (2^8).
 
While I'm sure this is true theoretically, keep in mind that we're talking about 24-60 frames per second. Not to mention having to come up with an algorithm that blurs the pixel in the direction of the movement. That's a lot of frames to analyze and entirely unnecessary if done right "in camera." Much easier to put a filter on unless you just like to spend time behind a computer screen.
There are smart motion blur filters available for the major editing suites which do exactly this. And as you said it is many frames to analyse and as a result it needs a lot of CPU/GPU power to run these kind of filters. They are heavy and slow. So getting it right in camera is till the bes way!
 

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