I have another question concerning recommended filters (if any) for our upcoming trip to Southern Utah and Grand Canyon. Some recommend an ND filters, others a circular polarizer, and still others suggest NO filters at all. This confusion brings me to this site. What do you suggest? If an ND filter, then what strength? If a circ. pol., how might it be used for best results where the red rocks are concerned? I plan to use a 17-50mm lens (on a 1.6 crop sensor camera) for a lot of my shots, as well as a 70-200/4 lens. Fortunately, both are 67mm. Yet, I don't want to purchase them if they will not get a lot of use. So are these filters a wise investment for this trip? As always, your suggestions, opinions, and comments are anxiously awaited. Thank you.