I drove to 360 Grandview around 8:30 AM and walked around for an hour enjoying the peace and quiet. The recent rains added some "life" to the stream so I used my Neutral Density filter and a trip to get some "white water" photos. But these photos were not taken at the Rock Mill Preserve. These were taken along Hollow Road just north of Camp Meeting Avenue. I pulled the car over, grab my camera, ND filter, and tripod, and walked down to the stream.
I spent about 30 minutes working on composition and lighting. At first, I used my Nikkor 35mm f/1.8 but realized that the Nikkor 18-55 f/3.5-5.6 would give me more choices. I had to run back to the car and get it.
Computing the exposure values for the use of an ND filter can be complicated. The Hoya NDx400 is a 9 stop -- "Big Stopper" -- ND filter. It's nearly impossible to focus once the filter is on the lens. Ed Velez told me about the PhotoPills app. This was my first time using it.
The app helped me easily calculate equivalent exposures with the filter in the available light. For example, without the filter, the exposure for the camera setting for correct exposure was at 1/13s at f/16. With the Hoya filter, the equivalent exposure was 17 seconds at f/16. I couldn't get 17 seconds on my D5100 I used 15 seconds or 20 seconds.
NOTE: The D5100 is a crop sensor -- APS-C -- camera. The full-frame equivalent of f/16 on APS-C is roughly f/10.33 which is approximately f/11. So I used an aperture of f/11 for these shots.