Sometimes we need you to provide us with calibration images to make sure we are getting the proper values for our distortion correction calculations. To learn more about the types of distortions and algorithms you can go to wikipedia. We need calibration images in the case of wide angled lenses usually. What you should do is take a picture of the following chessboard (or any chessboard image that will occupy the entirety of your monitor to make it easier) such that it will occupy the entirety of the photo's frame (you may need to right click the image and open it in a new tab):
You'll want to take a picture of the chessboard from 3-5 different angles, the following images are an example (there is text in the pictures explaining from what angle it was taken):
You can then send your images to email@example.com.