I got my projector used from a place that didn't know too much about projectors. There's a smear mark on the lens. I know not to use any chemicals or things like that, but could I use water and a soft cloth to get rid of that awful smear? Is there a way to get it clean or would I have to buy a new lens? Also, the contrast is fairly low (100:1) and the blacks aren't very good(almost grey, even when calibrated). Would getting rid of that smear help in blacks?