On the other hand, with color slide film to be viewed by projection, I think the center filter is a necessity with the 45mm lens. Shoot a roll with the 45mm lens without the filter and see what you think. You will know pretty quick whether or not you are willing to pay for the filter. If you are budgeting for the cost of an XPan and a 45mm lens, plan on paying for the center filter to go with it.