Practical ways to measure and correct distortion in industrial vision systems are discussed with an emphasis on ease of use. Tests were conducted that showed that significant amounts of spatial distortion can exist in commercially available camera/lens/frame-grabber combinations. Even solid-state cameras are not immune to this phenomenon. Substantial reductions in distortion can result from a locally affine correction scheme such as the one tested. Large numbers of control points do not seem to be necessary, although increasing the number of control points does result in increased accuracy up to a point. The correction scheme developed can be extended to calibration targets for which the control points are regularly spaced.>