However, the effect of the frame 124 is such as to limit the extent of the dark area and the result is therefore that the image stored in store 100 is as shown in FIG. 8I. The metal paths 52A do now not appear but, instead, two dark areas or features 134A and 134B appear, thus representing that part of the area within the frame 124 (FIG. 8H) in which the metal paths 52A are absent.