USAF-1951 Standard Target (T-20) Specification Document

This test target meets requirements as specified in MIL-STD-150A for resolving power tests. The target consists of a series of Elements having two sets of lines at right angles. Each set of lines consists of three lines separated by spaces equal to the line width. Each bar has a length to width ratio of 5:1. (Line width is equal to one half of line pitch, which is the inverse of line frequency.) Elements are arranged in groups of six each and Groups are arranged in pairs. Even numbered Groups occupy the left side and bottom right corner and contain a square feature having and edge length equal to the line length of Element 2 in that group. Odd numbered Groups occupy the top right corner and side