Graham can you tell us about the grad ND filters you are using. Are they screw on, size, made by purchased from and how used if not screw on.
Your photos are ... outstanding in the field. Really good.
Thank you very much! I'm very much a beginner, however I am more than happy to share with you the equipment specifics. Filters used include:
Singh-Ray 2-stop soft "Galen Rowell" ND grad
Singh-Ray 3-stop soft "Galen Rowell" ND grad
Singh-Ray 2-stop hard reverse ND grad
Singh-Ray 3-stop hard reverse ND grad
B+W 77mm 6-stop ND filter
B+W 77mm Circular Polarizer
I have two sets of filters, one is "P" and the other ix 4x6. I use a Cokin "P" filter holder and a Lee Foundation 4x6 filter for the larger ones. For long exposures I stack the filters and push the ISO down near 50 to increase shutter speeds.
If you're interested, here are some example images with the above mentioned equipment: