Champagne:Pancro Mirrored IRND set
The Pancros are my top pick for one very important reason...
They maintain the original character of the sensor regardless of density. Because they reflect exactly as much IR as they do visible light you can use them singly or in conjunction with other filters or Polarizers and the image is the same color and character as if you weren't using any ND at all. They also have no discernible color shift. If you have yet to purchase an ND set this is the way to go. They are expensive but not much more than a set of competing regular NDs (About $350 each filter). If you really want to cover your bases pick up a set of Panchro filters for outdoor use and a Tiffen or Rosco Hot Mirror for tungsten shooting."

Reflections on reflections...