click on the first image and s/he answers your question---as others said, ver very long exposures: Sonoma Coast State Beach -
The Summer months along the Northern California coast are usually thick, and grey. More days than not a thick marine layer sits above the beaches only moving out for a couple of short hours if at all. Recently there was a heat wave that moved through that pushed the marine layer off shore for the long weekend.
With the clear sky, and the sliver moon setting just after the sun I decided to put away the 10 stop ND filter, and wait for that magical edge of light. The quickly fading light can be difficult to work with. Metering the light to calculate exposure times is basically a waste of time, as the light has already changed by the time you dial in the proper exposure setting. On a completely manual camera system with no internal meter, there is not much to dial in. You don't have a choice of changing your film speed like you do with digital ISO settings. There are no 1/3 or 1/2 half stop shutter / aperture settings. I quickly gave up on trying to figure out the exposure times with the reciprocity failure of the film I was using, and went with my instincts. I set the lens to BULB, set the aperture to 16, locked down the cable release, and took a seat on the sand. I sat and watched as the light change with every passing second. Watching the light change on the sand, and the curling ocean waves, I somehow estimated the exposure time, and unlocked the shutter after 3 minutes. At this point a digital camera would reveal if my guesstimate was correct, but all I got was the sweet sound of the auxiliary shutter closing. I packed up my things and walked back to the car with a question of whether I was correct or not....