For years, I have been using a rotatable linear polariser to improve landscape photographs. They work very well at reducing the reflections from water, reduce the effects of haze and generally sex-up pictures. I thought the reason was quite simply that they reject on particular polarisation plane. The latest thing, on Photo Forums, seems to be the 'Circular Polariser', which is claimed to have a similar effect and which is marketed by Hoya, for example. These filters are also rotatable. I queried what they did and was told that they do the same enhancement of landscape pictures and that one could be used in conjunction with linear polariser to get cancellation (as with crossed polaroids) at a particular angle. You can produce circularly polarised light fairly easily with a quarter wave plate system but I don't see how that can select / reject one particular polarisation - because the E vector rotates to every angular value. Am I missing something here? Is it just an advertiser's way of renaming a Round, Rotatable Polariser as a Circular Polariser or is there some genuine effect here?