I recently satisfied an attack of NAS by purchasing a Sigma 18-50mm f/2.8. We are going on vacation to Washington, DC next week and I realized I needed a fast walk around lens for indoor shots at the Smithsonian museums, ( I also got a Manfrotto 679 monopod and 3232 head). Everything arrived fine but now I need a 72mm UV or MC filter. We only have Ritz cameras in my area and I've never been happy with their offerings--Quantaray or nothing. Does anyone know of a adorama-type camera store in Washington, DC or in the area of Stafford, VA? Right now I'm switching the 72mm filter between the 18-200mm VR and the Sigma 18-50mm, it's a pain.I hope to make the processes quick and painless so my wife doesn't get upset with "another purchase" and leave me stranded somewhere I'd rather not be. Oh, by the way, I also bought a 2GB memory card so I'd have enough space for all my shots, (it was a serious attack). Any help in this matter would be appreciated.