I've been taking a lot of photos lately with my wide angle lens (Sigma 10-20mm). While these pictures are great and I love them a lot, I'd like to remove some of the distortion that the lens introduces from them. I'm even creating a few panoramic shots from individual images that I've captured and the panoramas are coming out curved. They look like they were taken with a fisheye lens or something. I'd rather not have these types of photos include the distortion. In my city shots, the horizons are curved and the buildings seems to be leaning inward. Any advice would be welcome. Thanks.