The purpose of this test pattern is to measure the chroma sharpness both horizontally and vertically. This tells the viewer the chart format, e.g. 'PAL'. It can be used for raster registration check, 2D aperture correction symmetry measurement etc. They are useful for testing scan converters and vertical enhancers. They are useful for quick check of frequency response, testing 2D aperture correction devices and evaluation of cross-colour effects with conventional and comb type decoders.
All frequencies shown as tvls are in white text and frequencies in MHz are in black text.
This radial wedge covers spatial frequencies up to 450 tvl. The moving zone plate is especially useful for checking line or frame based comb decoders and scan converters performance. They allow display brightness and contrast adjustments to be easily made. For better visibility small boxes are accompanied by short higher contrast vertical lines. This last pulse is useful for ringing and echo measurements if equipment under test includes black clipper concealing distortions below black level.