ND Grad Calc helps you determine which neutral density graduated filters to use to take correctly exposed landscape photos. When using the suggested filters, the difference between the sky and the foreground will be around 1 stop.
Instructions
1. Meter the sky and foreground using spot metering on your camera. If your camera does not support spot-metering, use centre-weighted averaged metering.
2. Input the two shutter speeds into the app.
3. The app will suggest a filter to use, or the number of stops of filtration required.
4. Use the appropriate filter(s), and take the photo at the foreground shutter speed. The difference between the sky and foreground exposures will be around 1 stop in the photo.