1951 USAF resolution test chart

The design provides numerous small target shapes exhibiting a stepped assortment of precise spatial frequency specimens.

These 54 elements are provided in a standardized series of logarithmic steps in the spatial frequency range from 0.250 to 912.3 line pairs per millimeter (lp/mm).

The series of elements spans the range of resolution of the unaided eye, down to the diffraction limits of conventional light microscopy.

Commercially produced devices typically consist of a transparent square glass slide, 2 inches or 50 mm in dimension.

The slide is printed in metallic chromium by photolithography with the standard pattern, photographically reduced from a large master plot.