Hoya ND X400 82mm
Released for 82mm this gives a photographer endless possibilities. Please see the following article for advice.
http://www.redbubble.com/people/peterh111/journal/7983727-big-update-to-guide-to-nd-filters
In conditions of extreme light intensity, such as sunshine on snowy moutains or on the beach ND (Neutral Density) filters are recommended as essential.
Neutral Density filters are often ignored by photographers, but they have several uses and offer the possibility to achieve otherwise unachievable results. ND filters appear grey and reduce the amount of light reaching the film, they have no affect on color balance.