I have been looking for my first projector and found a used Epson 705hd that has been used only a few hours. Hoping to pick it up today. I have been reading some threads on the site regarind buying an ND4 filter. Can anyone tell me what this is used for? Also, I am trying to decide what type of screen and size to get. I have a space in my basement that I will be using that is 13 ft wide by 16feet. I did some measures for seating and the the closest viewing seat will be around 8ft and the other seating is between 12 and 15 feet. What size screen do you think would be best for viewing. I like to have some light when watching TV so can I get away with a white screen? I can control the lighting in the room. Thanks.