Accuracies obtained for the visual task of pointing or centring a circular black measuring mark on a circular bright target are presented. To understand the complex pattern of pointing accuracies, the shape of the image actually seen by the visual system is computed. This is performed by convolving the luminance profiles of the targets with point spread functions of the visual system, which estimate effects of image blur and lateral inhibition. The resulting luminance profiles are then analysed and simple visual criteria on which the pointing task is based are derived.