When does one use ND filters and why?

The title says it all. Is it just a way of cutting down on the light reaching the camera? If so I can see why it might be used in very bright places, but I don't see why they're used in normal photography. Can an expert please enlighten me? I know from other posts that many other people share my lack of understanding of the use of these filters.

There are a couple of reasons. The first is when you're trying to get a long exposure and it's bright out. The second big reason is if you want a narrow DOF when it's bright out- it means that you don't need to stop down to get the appropriate aperture.

A lot of landscape photographers also used graduated ND filters to make sure the entire scene is exposed correctly- if you don't have one the sky often tends to be overexposed, especially during sunrises/sunsets.

Using ND Filter to create special effects: An introductory guide

You can use one during a very bright day in order to control the highlight. As long as you can still maintain faster enough shutter speed with it, you can use it on your walk around lens. The main purpose is to doing a long exposure shot when motion blur is desirable such as capture flowing water or a rough sea, during early evening lighting condition. Depending at what stops the ND filter is rated. At 3 stops, you can get a 20 second exposure shot at F16 under ISO200 during early evening. At 10 stops, you can do the same thing properly during the middle of the day. When you capture moving water at 20 second exposure or slower, the water would become smooth and fog like. The effect is surreal...

Any waterfall photo where the water is smooth and milky are usually the result of a shot taken with a ND filter.

I have had some good luck with a 9 stop ND filter for long exposure shots in the daytime.

5dMk II
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PhotosGuy wrote in post #9865885
Using ND Filter to create special effects: An introductory guide

although i've known most of it already, this is still a great read.

Another application would be on a bright sunny day and you're using a strobe to balance out the sun. You need to get your shutter speed down low enough to allow it to sync properly.

Radtech has inspired me with that shot. this forum always makes me think in a different direction-thanks.

I used one for this so I could get a slow enough shutter speed on a bouquet of flowers in the sun.

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