SIO Reference 59-62. Dr. Morris and her staff at the Visibility Laboratory extended the war-time experimental approach to include studies of the visual detectability of separate pattern components and thereby achieved a successful solution to the patterned target visibility problem. The data for this study were collected and analysed and the theory described in this report was developed at the Visibility Laboratory ' during the period from August 1955 to December 1956. This basis for calculating visual detection ranges for nonuniform targets has been in routine use by the Laboratory since that time.