I agree wholeheartedly with Kerry. If you are using a mattebox, that filter is called the Schneider Tru-cut 680. Since it's a 'hot mirror', it must be the first filter light hits. You will have some green vignetting at wide angle (15mm and wider) but it's not too noticeable unless you're shooting in a room with light walls. It works beautifully to correct for the IR contamination.