We present a procedure for self calibration of a pinhole camera subject to radial distortion. Radial distortion parameters are estimated using a nonlinear least-squares approach based on the knowledge that the observed image originates from a set of equidistant control points lying on straight lines. The pinhole perspective effect is corrected by minimizing an error in the least-squares sense subject to nonlinear constraints. We illustrate the two-stage self-calibration procedure with numerical results based on state-of-the-art computing tools in nonlinear optimization.