Solid ND filters are designed to allow for longer exposures in any conditions, but particularly in bright light. Colours become fuller and details become richer. Running water (waterfalls, ocean tides) becomes smooth and misty as light information is written over and over during the exposure time. Clouds will soften and other moving objects will create blur while static objects remain pin sharp.
(Image on Left without filter – Image on Right with 6-Stop ND filter)