It doesn`t matter how clean your canopy is, the camera will still focus on it if it is within range. Hold your camera virtually touching the `glass`and you should be O.K.. Better still, shoot through the D.V. Panel. Dont forget that the viewfinder and the lens are not usually in the same place on a digital, if you don`t allow for it you can get the edge of the D.V.P. cutting through your piccie.
Mike W