RE: NEC PA271Q "Native" chromaticities
RE: NEC PA271Q "Native" chromaticities
- Subject: RE: NEC PA271Q "Native" chromaticities
- From: Roger Breton via colorsync-users <email@hidden>
- Date: Tue, 3 Dec 2019 09:34:47 -0500
Wow! Wayne, those guys knew how to make color 😊
No ICC profiling of any kind but they control over every element of the food
chain.
/ Roger
-----Original Message-----
From: colorsync-users
<colorsync-users-bounces+graxx=email@hidden> On Behalf Of Wayne
Bretl via colorsync-users
Sent: December 2, 2019 9:20 PM
To: 'Wire ~' <email@hidden>; email@hidden
Subject: RE: NEC PA271Q "Native" chromaticities
A bit of technical discussion about NTSC and television:
SMPTE had no influence as far as I know on the selection of NTSC primaries. The
choices were made mainly by RCA as part of the second NTSC (National Television
Systems Committee; the first NTSC established monochrome standards in 1941).
The standards, adopted by the FCC, simply stated that the signal should be
"suitable" for the specified primaries, with no details. Because the early
image orthicon cameras were noisy and used drift-prone tube circuits, it was
impractical to use matrixing of the R,G,B signals to match the primaries, and
as a result the camera optical filters were carefully chosen to match the NTSC
phosphors. They also used the old trick of film and print reproduction in using
narrow band color separation filters to enhance the saturation of ordinary
object spectra. The noise limitations also meant that it was unreasonable to
actually match the desired gamma correction of 1/2.2 (cameras were actually
designed to about 1/1.75), so that acceptable tone rendition was obtained by
careful exposure plus playing with the black level. The resulting signal gave a
high-contrast reproduction that was in a way similar to Technicolor, and
partially compensated for the low contrast ratio of early CRTs due to their
high screen reflectivity. However, the lowlight contrast was lost in the
process, and gradually improved as the display contrast ratios got better, and
rather dramatically when the image orthicons were replaced by the much less
noisy Plumbicon pickup tubes, plus gamma correction actually 1/2.2 and proper
color matrixing.
Even with these changes, there is typically a discrepancy between the
saturation capability of highlights and lowlights in subtractive vs. additive
systems, with subtractive systems (printing) excelling in lowlights, and
emissive displays excelling in highlights. The net result is that a display
with NTSC primaries, with correct black level and viewed under dim ambient, can
equal or exceed the gamut of most surface colors, whereas, an sRGB display is
lacking in at least the cyan and "true green" regions.
The compromise to Rec 709 is strictly because those were the primaries that
were available that made bright CRTs with nearly equal gun currents. The
unequal gun currents in early "NTSC" CRTs were a terrible headache in terms of
maintaining equal spot size and gray scale tracking between the guns. One
should also note that the psychophysical sensation of "colorfulness" is
affected greatly by display brightness, and the TV companies and their
customers recognized this, although they may not have had the research to
support it at the time. In any case, customers much preferred brighter
pictures, a difference they could see immediately and continually, while they
could not detect gamut limitations without seeing the TV side by side with the
program stage itself.
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