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ND filter usage
I have two questions (that may just need one answer)..

1. What is an ND Filter used for? I got one as part of a set that I bought for the circular polarizer and I have no idea what it is for..

2. Are they even used in digital photography or are they a relic left over from film?.

Thanks,Joe..

Comments (10)

A neutral density filter allows you to decrease the amount of available light, so you can slow down your shutter speed or open up your aperture, even when ambient light levels are high. A typical example would be to blur flowing water..

Used for film and digital..

Arthur.

Http://www.arthurmarshall.ca..

Comment #1

OutdoorArt wrote:.

A neutral density filter allows you to decrease the amount ofavailable light, so you can slow down your shutter speed or open upyour aperture, even when ambient light levels are high. A typicalexample would be to blur flowing water..

Used for film and digital..

Arthur.

Http://www.arthurmarshall.ca.

And there is also a "Graduated Neutral Density Filter" that is darker in one half (usually) than the other which is used to balance an exposure that contains large differences in brightness like balancing the exposure of a sky with darker landscape..

I suspect yours is as Arthur described and is uniform in density..

Nothing is enough for the man to whom nothing is enough...

Comment #2

OutdoorArt wrote:.

A neutral density filter allows you to decrease the amount ofavailable light, so you can slow down your shutter speed or open upyour aperture, even when ambient light levels are high. A typicalexample would be to blur flowing water..

Used for film and digital..

Arthur.

Http://www.arthurmarshall.ca.

Thanks, Arthur. So it sort of works like sunglasses for my camera? If I understand this right, the filter reduces the light that enters the camera which will cause the camera to readjust the settings for aperture and shutter. I think you are talking about using a manual mode and forcing longer shutter speed or wider aperture than the camera would normally select. In aperture priority or shutter priority mode, the camera adjusts the other parameter based on the users selection (in aperture priority the user sets aperture size and the camera adjusts the shutter speed accordingly based on the light). In full manual mode, the user can actually change the ratios between shutter speed and aperture size that the camera usually abides by. Is this the goal?.

I guess my confusion is this: if you can adjust the shutter length in S mode and the camera sets the aperture appropriately, you can achieve the blurred flowing water without the ND filter. How does lowering the amount of light that enters the lens help?.

I don't want to sound like I'm arguing with you and I'm not, I am sure you are right. I am just confused and want to understand this..

I appreciate your help.Joe..

Comment #3

Aletheia wrote:.

OutdoorArt wrote:.

A neutral density filter allows you to decrease the amount ofavailable light, so you can slow down your shutter speed or open upyour aperture, even when ambient light levels are high. A typicalexample would be to blur flowing water..

Used for film and digital..

Arthur.

Http://www.arthurmarshall.ca.

And there is also a "Graduated Neutral Density Filter" that is darkerin one half (usually) than the other which is used to balance anexposure that contains large differences in brightness like balancingthe exposure of a sky with darker landscape..

I suspect yours is as Arthur described and is uniform in density..

Nothing is enough for the man to whom nothing is enough..

Yes, Aletheia, I think mine is the uniform density variety.Joe..

Comment #4

To give you an example - shooting a waterfall in bright sunlight. To get a milky look to the water you typically need a shutter speed of anywhere between 1/10th sec and 2 sec. On the other hand you don't really want to close the aperture down to much beyond f16 because diffraction effects start to reduce sharpness at small apertures..

If the available light at f16 and ISO 100 gives you a shutter speed of, say, 1/50th, you have to reduce the amount of light hitting the sensor. Fitting a suitable ND filter will achieve this and allow you to reduce the shutter speed..

Note that this has nothing to do with Manual/Shutter Priority/Aperture Priority. You can use any of them, the problem is reducing the amount of light..

(Of course you can always come back on a cloudy day.)Chris R..

Comment #5

Chris R-UK wrote:.

To give you an example - shooting a waterfall in bright sunlight. Toget a milky look to the water you typically need a shutter speed ofanywhere between 1/10th sec and 2 sec. On the other hand you don'treally want to close the aperture down to much beyond f16 becausediffraction effects start to reduce sharpness at small apertures..

If the available light at f16 and ISO 100 gives you a shutter speedof, say, 1/50th, you have to reduce the amount of light hitting thesensor. Fitting a suitable ND filter will achieve this and allow youto reduce the shutter speed..

Note that this has nothing to do with Manual/ShutterPriority/Aperture Priority. You can use any of them, the problem isreducing the amount of light..

(Of course you can always come back on a cloudy day.).

Perhaps some day I will be able to create a cloudy day..

Chris R.

Thanks, Chris. I think I am starting to understand this..

You know, back when I didn't care, photography was a lot easier..

Joe..

Comment #6

Joe Abbiati wrote:.

Chris R-UK wrote:.

To give you an example - shooting a waterfall in bright sunlight. Toget a milky look to the water you typically need a shutter speed ofanywhere between 1/10th sec and 2 sec. On the other hand you don'treally want to close the aperture down to much beyond f16 becausediffraction effects start to reduce sharpness at small apertures..

If the available light at f16 and ISO 100 gives you a shutter speedof, say, 1/50th, you have to reduce the amount of light hitting thesensor. Fitting a suitable ND filter will achieve this and allow youto reduce the shutter speed..

Note that this has nothing to do with Manual/ShutterPriority/Aperture Priority. You can use any of them, the problem isreducing the amount of light..

(Of course you can always come back on a cloudy day.).

Perhaps some day I will be able to create a cloudy day..

Chris R.

Thanks, Chris. I think I am starting to understand this..

You know, back when I didn't care, photography was a lot easier..

Joe.

It's true about anything; the more you care the harder it gets..

Nothing is enough for the man to whom nothing is enough...

Comment #7

Joe Abbiati wrote:.

I have two questions.

Joe, a few years back, I was asked to explain a little about shooting flowing water on a sunny day, and having it turn out all nice and smokey-looking. My response touched upon the use of neutral density filters (among other things). I'll re-post it here..

BEGIN TEXT:.

The "Sunny f/16" rule says that on a nice, sunny day, the proper exposure will be around 1/ISO @ f/16. This isn't precise to the fraction of an f-stop, but it'll put you in the ballpark..

So let's call the baseline exposure for a photo of the stream to be 1/125 sec. @ f/16. (I'm assuming you've set the camera to ISO 100, and I'm rounding the 1/100 sec. to 1/125 sec., since 1/125 sec. is a "classic" shutter speed from the olden days, and many photographers find it more comforable to think in terms of 1/125 sec. than to think in terms of 1/100 sec.



Well, you want the water in the stream to look all misty and smokey, right? Can't get that at 1/125 sec., unless the stream is a raging torrent of water rushing along at 100mph and sweeping away everything in it's path. For argument's sake, let's assume that it's a gentle little stream, where the water flows lazily to the ocean, and not something out of a disaster movie..

Now, in order to get the water looking all flowing and all, we're going to have to use a shutter speed of around 2 seconds. How do I know this? Experience. I've photographed lots of streams, and 2 seconds works out about right, much of the time. If you think 1/4 sec. looks better, or 16 seconds looks better, fine. But for purposes of this explanation, we're going with 2 seconds..

So, we go "125...60...30...15...8...4...2...1...2s," and realize that a shutter speed of 2 seconds is exactly 8 stops more than the indicated shutter speed of 1/125 sec..

Which means, we can simply close down the lens by 8 f-stops, and it'll balance out extending the shutter speed by 8 stops in the other direction, and net exposure will remain unchanged. Everything will be properly exposed, and the water will have that neat look we want..

Problem is, we can't close down the lens by 8 stops, because the smallest aperture the lens offers is f/22, which is only 1 stop smaller than f/16. Not 8 stops smaller. Besides, even if we could close it down to f/256 or whatever the ungodly tiny f-stop would have to be, diffraction effects would leave us with a really crummy image. Darn laws of physics. (Personally, I don't even like using f/22, unless the situation really demands an f-stop that small. Although in some macrophotography situations the increased depth of field of a tiny stop like f/22 is worth the reduction in resolution due to diffraction.).

Okay, no problem. Instead of closing down the lens by 8 f-stops, we'll simply reduce the camera's ISO setting by 8 stops. So we count "100...50...25...12...6...3..." and soon realize that we'd need an ISO of, like, 0.3, to cut ISO 100 by 8 stops, and that's just not a possibility, either..

What to do, what to do? I'll tell you what to do - we're going to use neutral density filters..

A neutral density (ND) filter does for your camera, pretty much what dark grey sunglasses do for your eyes. It cuts the amount of light way down, while leaving the colors unchanged. (The "colors unchanged" part is why I specified grey glasses, and not amber or green or some other tint.).

So we try to order an 8-stop ND filter from B&H, only to find that they don't have any 8-stop ND filters. But they are willing to make us a sweet deal on a 5-stop filter and a 3-stop filter. As a 3-stop and a 5-stop can be used together to equal 8 stops, we go for it. After all, having a 3-stop filter and a 5-stop filter is propably going to be more versatile than an 8-stop ND filter would be, anyway..

The filter arrives, and we head on down to the stream. It's a sunny day. We put the ND filters on our lens and....

What's this? The lens won't autofocus! And the exposure meter is acting sort of wierd, too..

You see, your camera has difficulty autofocusing and determining exposure when that much light is cut. The thin trickle of photons hitting it's sensor isn't quite enough to permit normal operation..

So here's what we do - we meter without any ND filters on the camera. The camera says the proper exposure is 1/125 @ f/16. We remember this..

Then we let the camera auto-focus, and next we switch the lens to manual focus, so it'll keep using that focus distance, and not start hunting for proper focus once the ND filters are in place..

Oh, and did I mention that the camera's on a solid tripod? Because it is. Believe me, you don't want to take 2 second long exposures handheld, unless you find blur to be artistic and aesthetically pleasing..

Now, we screw on the 5-stop ND filter, and the 3-stop ND filter..

Next, we remember "1/125 sec. @ f/16," and mentally subtract 8 stops from that, to get 2 sec. @ f/16. We set the camera to Manual exposure mode, and set the shutter speed to 2 sec. (which looks a lot like 1/2 sec., so be careful), and the aperture to f/16..

We then take the picture, preferably using a remote release or a self-timer..

And we get to thinking, "Maybe the water would look better at 1 sec., or 4 sec." After all, it's hard to predict exactly how long an exposure will yield that nice, misty, flowing water look. These things are more of an art than a science, you know..

So we bump the lens aperture down one stop, to f/22. And consequently increase shutter speed by one stop, to 4 seconds. Then we open the lens up to f/11, and set the shutter speed to 1 sec. See, all this keeps our total exposure constant; whenever we go in one direction with one setting, we go the exact same distance in the opposite direction with the other setting..

The result looks a little like this (taken at Bushkill Falls, PA, USA, with a Canon G3 camera):.

Image control:Zoom outZoom 100%Zoom inExpand AllOpen in new window.

Boy, we're good...

Comment #8

-The ONLY time I have used a ND filter was for fireworks. Many digital cameras only stop down to f-8. You need one or two stops darker to keep the colors from washing out and becoming pale. Thus you can get the required f-11 and f-16.Gene Smith..

Comment #9

All the replies are correct but there is another use for ND filters. They can be used when you wish to use a very large aperture to reduce the depth of field and blur the background so it is less distracting, but have too much light so the fastest shutter speed available is insufficient to provide the correct exposure..

A ND filter will allow you to use a large aperture and get correct exposure by bringing the shutter speed down to what your camera is capable of...

Comment #10

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This question was taken from a support group/message board and re-posted here so others can learn from it.

 

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