I hiked out to Taughannock Falls in the middle of the day with the idea of getting a long exposure photo of the falls. Sounds crazy but I did have a plan. Upon arriving, I set up the Nikon D700 camera and Nikon 24-120mm f/4 VR FX Lens on a tripod and used Aperture mode set to f/16. This gave me a shutter speed of 1/60th of a second at ISO 200.
At this shutter speed, you can see all the people walking on the rocks in the creek and up by Taughannock Falls. Using f/16 got me sharp focus from front to back. The water falling looks frozen.
I left all the settings the same and put a 3-stop Neutral Density (ND) filter on the lens. This increased the shutter speed to 1/5th of a second.
We start to see motion blur in the people walking on the rocks and the falling water is starting to get the smooth look of long exposure photos of waterfalls.
Back to my plan, I replaced the 3-stop ND filter with a new B+W 77mm 3.0 ND 110 Filter which is rated at 10 stops. Using this very dark filter, it is impossible for your camera to use auto-focus and just as impossible to focus manually. Focus your camera without a filter first and then turn off auto-focus before putting the filter on.
Ah, there is the silky looking waterfall photo I was looking for. You will notice most of the people have disappeared as they did not stay still long enough during the thirty second long exposure.
Think of the possibilities here for amusement park rides, moving vehicles and fireworks..oh, fireworks!