A ND filter would not work for me since it reduces white as much as black. The image would be too dim on my 3.5m wide 16:9 screen. Only even bigger On-Off contrast helps here. The colors can be dialed in 100% with the CMS of a Lumagen Radiance, by the way.
yeah the light output is cut severly, it ended up perfect for my smaller screen size but I couldn't see a ND4 filter fitted unit doing any bigger, the upcoming JVC RS-VP2 (VP50pro rebadge) will take care of the colors as well, maybe we will see the control come to the DVDO VP50pro as well