Anyone use such a device? (Beseler, part # p112) Im thinking of buying one from ebay... and the claim is that it shortens exposure times, as well as yields sharper prints... I can imagine that I understand the physics behind it... point light sources give us the sharpest shadows. . . which is really what we are projecting on to the paper under the lamp house.... but... anyone use one? your experiece - ? TIA.