At some point in a photographer’s life, he or she will want to try neutral density photography. What is it and why do I want to try it? Neutral Density simply means using a filter to reduce the amount of light entering the lens. This allows for longer exposure times, especially during daylight hours, allowing you to blur moving objects in the frame such as moving clouds or water. Clouds or smoke will appear in the frame as the streaks they leave going across the sky rendering an eerie look. Water will tend to flatten and smooth out, and if the exposure is long enough the water will become misty looking. (See the picture to the right)

The Equipment: If you are a photographer with a nice Nat Geo budget I would recommend getting professional square glass ND Filters such as the Cokin Pro or Lee Big Stopper series. They are much easier to use in the field because they do not have to be screwed to the lens, however they carry a hefty price tag. If you’re the frugal photographer such as me, you will end up getting the round screw-in type filters. Neutral density filters come in different strengths, so which one(s) should I buy? The numbers can be confusing so here is the scoop. I have a weak density filter (Hoya 4 stop ND), a medium heavy density filter (Hoya 9 stop) and what they consider a heavy density (B+W 10 stop), which allows almost zero light in. You may need all three at different times of the day with different light levels to achieve the blur that you are looking for. Remember also, the filters can be used stacked or in combination with a circular polarizer to get the density down even further.
The Neutral Part: Density means the amount of light the filter blocks, but the Neutral part refers to the ability of the filter to do this without affecting the color. Many ND filters, even the expensive ones will leave a colorcast to the pictures. This sometimes can be removed in post processing, but not always. I can’t afford it but I have heard that the Lee Big Stopper, which is the most popular, leaves a blue cast. I know for a fact that the B+W ND filter leaves a brown cast to all its pictures which sometimes cannot be removed. The best neutral filter brand that I have found is Hoya and it just happens to be one of the less expensive ones.
The Process: I started out with the B+W 10 stop ND filter and varied my exposure times. I quickly found this to be a hit and miss deal on correct exposure times to use, with a lot more failures that successes. I heard that there were mathematical formulas that I could use to figure the proper exposure times but not being a math genius or fan, I took my ND filter and threw it in the bag never to be seen again. Then one day I was reading an article by world renowned waterfall photographer Kevin Adams where he mentioned that now “There is an App for that”. The App he referred to was the NDTimer by Three60 Software. It's free but unfortunately, it is only available for iphone at the present time. It is extremely easy to use and requires no MATH. Simply set your camera to the f-stop and/or shutter speed you would use for the scene as you would shoot it normally. Focus the camera and then switch it to the manual focus mode. In the App, input the shutter speed from your camera and the filter or combination of filters you are using. This will tell you how long to keep the lens open for the perfect exposure. Screw in the filter or the combination of filters to your lens, turn your camera to bulb mode, start the app on the phone, (has its own built in timer/alarm) and hold down your shutter remote until the time runs out and the alarm sounds. Bingo/Presto, the perfect exposure. (Well almost, that’s what Photoshop is for)To vary the results, simply change the ISO speed or f-stop and go through this process again.
My Recommendation: I would start with a 4 stop ND, a 9 stop ND, and a good circular polarizer. Don’t forget they can be used in combination if needed, but when stacking filters there is always a chance of some vignetting. The App or one like it for Android phones is a must have unless you have a craving to do math while chasing that sunrise. A flashlight is also good to have if you arrive before first light or stay after dark. Some tell you to carry gaffers tape to cover your viewfinder from stray light, but I have not found this to be a problem. This is a lot of “Things” to fumble with especially if you are working above rocks, or sand on the beach, I would recommend getting something like the Vanguard SB-100 stone bag to attach to you tripod legs to hold your gear while shooting. It is cheap, easy on-off mount, and keeps you from dropping your gear to the deck. Find a local pond, lake, or just start practicing in your front yard today. You will get better at every attempt.
P.S. Needless to say, but I will preach it anyway: Always use a sturdy tripod and remote release during ND Shots. The camera MUST NOT MOVE !