I bought a Center density for the 45. The focus is really strange, not really sharp almost a double focus. I've found it easier to shoot past f11 and carry a monopod for slower shutter speeds. The weird focus combined with 1 stop loss of light really makes the center density kind of useless. There is a definate image circle fall off that if you don't want it willl dissapoint once you see the film.
Stop trying to get into my mind, There is nothing there!