I attended the Adirondack Balloon Festival yesterday, and used my Sigma 10-20 and Circular Polarizer for the first time in several months. While many of the images came out fine, many others came out like this: As you can see, the sky is very uneven - a consequence of using the CP filter improperly, I think. This unwanted effect happened with every shot taken with the sun off to the right. Time of day was perhaps 40 minutes before sunset. What would be the best way to correct the uneven sky in NX2? Note: While the original image is NEF, this image is a JPG just for posting here. It is straight out of the camera with no post-processing at all. Any help would be appreciated.