It's amazing what you can do with a ND 400!
The ND 400 is a neutral density filter which reduces
dramatically the intensity of light entering the camera (loss of 9
stops), which allows long exposures at any time of day.
So, during a sunny day on a beach, you can consider images with
exposure time up to 30 seconds easily. Everything that moves during
the long exposure time will blur or absent from the photo (clouds,
water, waves, people,...)!
However, due to the very low light entering in the camera, most
of DSLR's automatisms do not work (autofocus and light metering).
The use of ND 400 is quite delicate and requires many manipulations
to achieve his ends.
The basic technique (...)