THE PERCEIVED ORIENTATION OF ALIASED LINES

The use of raster display devices for the display of graphics causes p roblems of aliasing when edges of lines are produced. This can be sign ificant in those psychophysical experiments where the orientational pr operties of the stimulus are important. We have assessed the perceived orientation of a selection of aliased lines by comparing them with th e orientation of pairs of dots. It is found that the perceptual orient ation is modelled well by a least-squares metric on the pixels that co mpose the line. Small deviations from this metric were found, and were also found ina control experiment employing anti-aliased lines. They appear to be due to range effects. Averaged across subjects, orientati onal acuity was only slightly lower for aliased lines.