Long exposures are like art projects. The goal is to capture stationary objects while blurring or smearing moving elements like water and clouds. You can stack 3-stop and 10-stop neutral-density filters to take long exposures (two to five minutes or longer) in bright daylight. I use this table to determine my exposure. Be sure to add an additional 10 seconds for every stop over 10 stops. With film you have to adjust for reciprocity failure. The shot above of the Seattle skyline and Elliott Bay at minus tide was about a four-minute exposure. A couple kayakers paddled in front of me during the shot but moving objects don't show up on film. I hiked several miles to reach Middle Wallace Falls near Gold Bar, WA. My wife held a magazine over my DSLR to shield it from rain as I snapped this 10-second exposure.
FILM CAMERA MAMIYA 645 FILM FUJI NEOPAN ACROS 100
DIGITAL CAMERA NIKON D200