This app allows the user to explore the effects of the different lens distortion parameters (3 radial and 2 tangential) of a common camera lens distortion model. This is model is used by both the Camera Calibration Toolbox:
This tool allows the modification of the 5 distortion parameters (k1, k2, k3, p1, p2), the 2 focal lengths (fx, fy), and the camera center (cx, cy). It allows the user to use one of two built-in images or to load a custom image.