Sony G90 manual Color and Hue, Adjustments, Avia Guide to Home Theater pro

linear will be dis-		V I D E O		the primaries with-
cussed at another				out changing their
time, but with the availability of digi-			levels for the white color. It is
tal signal processing, such transfor-			adjusted until the signal levels of
mations are practical, but expensive.			each primary alone matches its sig-
Some approximate	corrections can		nal level, and therefore brightness,
be made more simply on consumer			in white. The Hue control varies the
displays.			relative signal levels of the primaries
			to each other, except in white, so
			that the brightness of any one pri-
7. Color and Hue			mary is the same in two complemen-
Adjustments			tary colors. For instance, the bright-
I have shown that color accuracy is a			ness of green should be the same in
			yellow as it is in cyan. When the sig-
function of grayscale and phosphor
			nal format conversion to RGB is cor-
accuracy when a monitor is driven by
			rectly calibrated, the brightness of
RGB signals. However, no video
			any one primary will appear the
sources produce RGB signals direct-
			same everywhere it is used in the
ly. Instead we have composite, S-
			color bars.
Video, or YPbPr component video
			On many consumer monitors, it
from our sources. These signal for-
			is not possible to adjust the Color
mats must always be converted to
			and Hue controls for the proper
RGB signals to drive the display
			results. This means that the conver-
device, either in a TV monitor or per-
			sion circuits are not capable of being
haps externally in a line doubler, or
			accurately calibrated to generate the
other upconverter, to drive a projec-
			correct RGB signals. This can be an
tor. This introduces another source
			intentional decision by the manufac-
of color errors. Hue and Color con-
			turer who believes that the resulting
trols are usually provided to calibrate
			colors, although inaccurate,		are
the conversion from the source sig-
			more likely to attract purchasers.
nal format to the RGB signals.
			Conversely, Sony now includes addi-
Color bars are used to adjust
			tional service level adjustments in
Color and Hue because we know
			its top-end products to improve the
that the three RGB signal values
			conversion and color accuracy.
should be the same everywhere
			However, it should now be appar-
they are used in the color-bar pat-
			ent that even if the color decoding is
tern. Therefore, with proper cali-
			adjusted correctly, the colors will still
bration, the same brightness of blue
			not be accurate unless the grayscale
light should come from each color
			is properly adjusted and the phos-
that contains blue (blue, white,
			phors match the SMPTE standards.
cyan, and magenta). The same is
			The blue-filter method works perfect-
true for red or green. Remember
			ly for professional broadcast moni-
that the brightness of red, blue, or
			tors be-cause the latter condition is
green is different and that was set
			satisfied. In consumer monitors, this
by adjusting the white color tem-
			method will produce colors only as
perature. But the brightness of any
			accurate as the phosphors and con-
one primary should be the same
			version circuits allow. A highly
everywhere it is used in the pattern,
			knowledgeable	calibrator,	who
including white.
			understands all the concepts we’ve
Using this principle, calibration
			discussed, can use a color analyzer to
DVDs like Video Essentials and the
			adjust all parameters and achieve
AVIA Guide to Home Theater pro-
			better color accuracy. For this rea-
vide filters (blue in Video Essentials
			son, the blue filter method must be
and red, blue, and green in AVIA) so
			considered an	approximation	for
that the light from only one primary
			consumer monitors. The AVIA DVD
can be viewed at a time. Most CRT
			provides an additional test pattern
projectors provide a means to turn
			that can aid in fine tuning the Hue
on one primary at a time (or you can
			and Color adjustments, but that is the
cover the lenses), so filters are
			best a user can do without expensive
unnecessary. The	Color saturation

control adjusts the signal levels of

instrumentation.