I've tried multiple exposures as described in Les McLean's book; but have a few problems. All my LF lens are old. Their slower shutter speeds appear to be off by alot. And they all require manual cocking. I would think the manual cocking would jar the camera enough to blur the image, even when on a sturdy tripod. Since my exposure times are long ( several seconds), was thinking of using a black hat, etc., to cover lens between exposures. Any suggestions?