What do you do if you don’t have a ND filter that is a Neutral Density filter to allow your camera to take long exposures in daylight and thereby blur water for those dreamy waterfall or seaside photographs.
Well one technique is to take a number of photographs from a tripod of the scene. It has to be on a tripod so that each shot is the same except for the moving water. The more shots the better, well up to a limit of say 30 and then blend them if Photoshop or Gimp. Now the blending technique can be any way you want as long as the shots are all in layers.
As an example I took about 34 shots of this beach scene at a spacing of 15 seconds. Now this spacing is too long as it produces posterisation in a clear sky or in this case bands in the clouds. However despite the banding one can see that it is effective in producing a beach scene the same as a long exposure.
For the averaging one can blend normally and for each shot calculate according to this formula %blend = (1/number of shots +1)*100 It does work. For the shot below I just took 10% for each and then blended with soft light mode in photoshop. Most ways of blending will end up near this, experiment and have fun.