DigitalVideoAndHDTVAlgorithmsAndInterfaces.pdf

Table 22.2 NTSC primaries
(obsolete) were once used in
480i SDTV systems, but have
been superseded by SMPTE
RP 145 and Rec. 709 primaries.
EBU Tech. 3213, EBU standard for
chromaticity tolerances for studio
monitors (Geneva: European
Broadcasting Union, 1975; reissued
1981).
Table 22.3 EBU Tech. 3213
primaries apply to 576i
SDTV systems.
different from those “on the books.” So although you
may see the NTSC primary chromaticities documented
– even in contemporary textbooks, and in standards
for image exchange! – they are of absolutely no
practical use today. I include them in Table 22.2, so
you’ll know what primaries to avoid:
Red Green Blue
White
CIE Ill. C
x 0.67 0.21 0.14 0.310
y 0.33 0.71 0.08 0.316
z 0 0.08 0.78 0.374
The luma coefficients chosen for the NTSC system –
0.299, 0.587, and 0.114 – were chosen in 1953, based
upon these primaries. Decades later, in 1984, these
luma coefficients were standardized in Rec. 601
(described on page 291). Rec. 601 is silent concerning
primary chromaticities. The primaries in use by 1984
were quite different from the 1953 NTSC primaries. The
luma coefficients in use for SDTV are no longer
matched to the primary chromaticities. The discrepancy
has little practical significance.
EBU Tech. 3213 primaries
Phosphor technology improved considerably in the
decade following the adoption of the NTSC standard. In
1966, the European Broadcasting Union (EBU) standardized
576i color video – then denoted 625/50, or
just PAL. The primaries in Table 22.3 below are standardized
by EBU Tech. 3213. They are in use today for
576i systems, and they are very close to the Rec. 709
primaries that I will describe in a moment:
Red Green Blue White, D65 x 0.640 0.290 0.150 0.3127
y 0.330 0.600 0.060 0.3290
z 0.030 0.110 0.790 0.3582
The EBU retained, for PAL, the well-established NTSC
luma coefficients. Again, the fact that the underlying
primaries had changed has little practical significance.
238 DIGITAL VIDEO AND HDTV ALGORITHMS AND INTERFACES