1) What is the need for using a NC filter which as stated in the manual is a must, when it is only a protective filter and I cannot understand what it is supposed to protect since it is embedded right in the middle of the lens. 2) The manual also recommends the use of a optional Circular Polariser. How is one to use a polariser when it is not possible to rotate the ring ? Does it have to be left at 1200 position ? Will appreciate if some user can clarify these queries, thanks.