Hi! I recently bought a Canon 10d and am just learning how to use it. I added a 50mm and a 17-40mm with a pretty inexpensive UV filter. Eventually, I hope to add a telephoto zoom and would like to before my trip to Thailand in March, but I'm not sure I can afford the trip and a lot of new gear. I'm pretty sure I should get a polarizer, although I don't know anything about them...I've heard there are different kinds. Can you give me any suggestions on which lens to buy the polarizer for and what kind of polarizer? Any other ideas on what to add to my gear, how to travel with it, etc, would be appreciated. As for subjects, I'll be spending several days at the beach and the rest of the two weeks in Bangkok and Chiang Mai. Thanks for your help!