As shown by L. D. Harmon of Bell Labs, it is difficult to recognize faces when they are shown in a coarse grid of intensity modulated blocks. When spatial frequencies above the basic grid frequency are removed (filtered out), the recognizability improves tremendously. In Nuclear Medicine, we are being presented with pictures of relatively coarse structure. In these, we are looking for "unknowns"--lesions that might exist or unusual shapes of organs. So, it is even more important that the eye does not get distracted by structure (= noise) in the picture which is not inherent with the distribution of radioactivity in the patient. So far, pictures generated by computer from an X-Y array of numbers have had a lot of spatial frequency noise. Continuous Tone Image (CTI) developed at Baird Corporation, is a computer-generated analog display for its gamma camera.