I was saying about pola screens, and it's the one... the one filter that I will always have with me when I'm shooting on exteriors, and I use... I had a pola screen that was combined with an 85, so that it was all in one piece of glass. I never liked putting too many pieces of glass on the front, especially if you're using a zoom lens, because you get a sort of internal reflection building up sometimes and unwanted flares with more and more pieces of glass. So I used a pola screen combined with an 85, and I was saying it’s the one filter in which you can increase the contrast by cutting down the mist. But if you were using it say, with a sun flare on the water, then it would reduce the contrast by rotating it. And you... you can determine how much you want to reduce it. And I think it's the one filter which gives you enormous possibilities of control on location. I have used it very occasionally on interiors where you've perhaps got a reflection, a glass or something or a window that you've got to get rid of. But of course with a pola screen you lose nearly two stops, and on interiors to lose nearly two stops is quite a disadvantage. Whereas if you're shooting, say on a sunny location where you would perhaps be shooting at 16 and you don't want to stop down that far, by putting on the pola screen you can open up nearly two stops to more like eight, which is sometimes a... more of a stop you want to work with, you know, because the stop you're working at affects the depth of field. It depends how much depth of field you want to achieve.