Why You Need a Neutral Density Filter
Neutral Density filters can be a photographers best friend when you want to get creative with depth of field or long exposures but there is simply too much ambient light. Take for example that gorgeous waterfall that you want to use a longer exposure with to get that silky look to the water. To get that look we need to use an exposure of 1/2 a second. If We use the Sunny 16 Rule, the right exposure would be ISO 100, 1/100th shutter, and f/16. But if we wanted 1/2 second exposure, we cant take our ISO down anymore (on most cameras) and if we crank our aperture to the maximum of f/32, we only gain one stop which would take us down to 1/50th of a second, nowhere near slow enough to smooth out that water. However, slap a Neutral Density filter on the camera that can block 4 stops of light and you are right where you want to be to get the shot.
If you are shooting video, shutter speed on your video camera is very important to have a realistic looking scene. Too slow and you get smearing, too fast and it looks jumpy. Since you want to stick to very specific shutter speeds with video, an ND filter can really be useful with shooting video.
Make Stuff Disappear
A trick I learned a long time ago from another photographer (I wish I could remember who) was to use long exposures in situations where there are lots of people or other moving objects that you don’t want in the scene. A long enough exposure will essentially remove the moving objects from the scene. The following is a very simple example of this technique.
In the first photo you see a typical freeway, without an ND filter I dropped the ISO to 100, pushed the aperture to f/32 but I could only get the shutter speed to 1/13 of a second. With these settings all we get is motion blur from the cars.
In the next shot I installed a variable ND filter and set the shutter to 1 second and opened the aperture to f/11 to try to pick up more sharpness and then adjusted the filter to get the exposure I wanted. We can still see some blurring of the cars on the freeway but the freeway is starting to look more empty.
In the final image I adjusted the shutter speed to 2.5 seconds and then adjusted the variable ND filter to set the exposure. With this longer shutter speed the cars on the freeway simply vanish. You can do this trick only when objects or people are moving. If you tried doing this at the Lincoln Memorial in Washington DC you wouldn’t eliminate anyone that was sitting on the steps reading, but if everyone was in motion then it would work.
Buying ND Filters
The problem with buying ND filters is that you would often want to have 4-6 different ones to handle different situations. The other option is expensive variable ND filters such as Fader variable ND filters that have traditionally cost upwards of $150 and higher.
More recently we have seen very low cost variable ND filters from companies with pretty good reputations such as Neweer. I recently ran across the latest Neweer Variable ND filters running between $6 – $20 depending on the size. I know that is an incredible price difference so I went and ordered some for myself for comparison and will be doing a review as soon as it arrives. If you are looking for some ND filters, I think you should consider the Neweer ones to get started with, even if there is a small color cast it should be easily fixable in post production.