National Park wrote:
This method might work well if my camera would focus with the ND filter on, but my camera often won't focus properly with a dark ND 10 filter on. Since I usually have to take the filter off in order to properly focus, I then take the shutter reading and use an app on my phone to determine the correct shutter speed when I put the filter on. Thus, the method in this video may not be very useful to me. But I will give it a try.