# Image Distortion

Images acquired using a camera and lens usually exhibit these types of distortion:

- Aspect ratio distortion caused by non-square pixels
- Planar perspective distortion caused by the camera being off-axis
- Radial distortion caused by the optics in the camera lens

Note: The distortion shown in this figure (and others in this topic) is exaggerated. While the Checkerboard calibration tool can easily handle the degree of distortion shown in these illustrations, it is typically used to correct less distorted images.

In most cases, the distortion present in an acquired image is a combination of the three types of distortion shown above:

The difference between two images caused by aspect ratio distortion is linear; it can be described by a system of linear equations and represented by a CogTransform2DLinear object. Perspective and radial distortion are both nonlinear. The difference between two images caused by these types of distortion cannot be represented by a system of linear equations.

Note: Nonlinear calibration cannot be used to calibrate images that have been stitched together from multiple acquisitions. Only images acquired using a single exposure exhibit the type of distortion that this tool can correct.