Assertion: palette | /r/HasProperty | built for pure grayscale
Facets:
value: based on four luminance values
type: OTHER
Source sentences:
text: With the NTSC format, a 128-color palette was available, built based on eight luminance values and 15 combinations of Pb and Pr chroma signals (plus Pb = Pr = 0 for a pure grayscale):
text: The 56-color palette is built based on four luminance values and twelve combinations of Pb and Pr chroma signals (plus two series of Pb = Pr = 0 for several pure grays).