Test chart
From The Glossary of Digital Photography
A chart used for testing lenses. It has pairs of lines printed increasingly closer together. To check the resolving power of the lens, the test chart is photographed. The test chart can be used to check the resolution of the camera and lens. A specific chart, called the I3A/ISO Camera Resolution Chart, is used for digital cameras. The resolution is measured in line pairs per millimeter or lines per picture height. Other test charts are designed to measure optical aberrations; there are also special charts for microphotography, scanners, projectors, and digital video cameras.
