Yamaha DPX-1100 - Manual (Page 5)

The WRGB and WRGBYCM modes are
factory preset with the Rec. 709 high-defini-
tion primary colors. Yamaha should include
the Rec. 601 color values as another preset
choice, but you can enter them yourself. It
is rather complex to compute the (x,y) coor-
dinates of the complimentary colors, so I
created a table for you with all of the (x,y)
color coordinates for Rec. 601 and Rec.
709. A gain (brightness) adjustment is also
provided for each color. The DPX-1100 can
automatically adjust the gain of the individ-
ual colors, or they can be manually set using
the red, green, and blue filters supplied with
the AVIA: Guide To Home Theater or Digital
Video Essentials.
The DPX-1100 Color Adjustment system
is an exceptional feature. It is easy to direct-
ly enter values for a colorimetry standard
(i.e. Rec. 601), or to use a color analyzer to
adjust the values to optimize their accuracy.
But it’s cumbersome to manually copy all of
the entries from one memory to another if
you use multiple inputs. A memory-to-mem-
ory copy function would solve the problem,
or the Color Adjustment values could be
saved in global memories that could later
be assigned to specific input memories.
Gray Scale Accuracy
The Color Adjustment function provides
the means to adjust the white reference at a
single video level. To achieve accurate
color reproduction, the white reference must
ideally remain at D65 for all brightness lev-
els from 0-IRE (black) to 100-IRE (peak
white). That ability is called gray scale
tracking. Most projectors provide gray
scale-tracking controls (RGB offset and
gain) that apply to all input signals. The
DPX-1100 only provides those controls
(Level Adjustments) for analog RGB signals,
and relies on fixed parameters to provide
acceptable gray scale tracking for HDMI
and other analog signals. Fortunately, the
DPX-1100 gray scale tracking still per-
formed very well. (Level Adjustments are
also provided for analog YPbPr signals, but
those only affect color decoding and not
grayscale accuracy.)
I tested the HDMI input first. I used the
Color Adjustment function to set the color
temperature to 6500K, and because D65 is
just above the blackbody curve I set the ‘uv’
value to +0.002. I was pleasantly surprised
when the 75-IRE gray window measured
(x=0.314, y=0.329), which is almost exactly
the x,y coordinates (0.313, 0.329) of D65.
But I was even more pleased that the gray
scale measured 6500K +144/-130K from
20-IRE to 100-IRE, and most importantly the
dE value was 2 or less over most of the
gray scale range and only 6 at 10 IRE. The
dE value expresses the distance from D65
in a color space that is perceptually more
uniform than the CIE x,y color space. A dE
value of 1 is the just noticeable difference
(JND), but values of 3 or less are negligible
differences in most practical situations.
The analog YPbPr input also produced
good gray scale tracking. The dE value was
2 or less over most of the grayscale range,
increasing to 4 at 100-IRE and 6 at 10 IRE.
These results are included in the Gray Scale
Tracking table. You can see in the chart that
color temperature alone is a fairly poor indi-
cator of gray scale accuracy. The 100-IRE
color temperature is much closer to 6500K
for the YPbPr input compared to the HDMI
input, but the perceived color error is larger
(dE of 4 versus 1).
I used the Level Adjustments that are
provided for analog RGB signals to improve
the gray scale tracking at the darker levels.
The dE value at 10-IRE improved from 6 to
3. I could also have improved the tracking
at 100-IRE (dE = 4) by reducing the peak
white output slightly, but I was already
pleased with the results. My calibrated set-
tings for the analog RGB input measured
6500K +22/-70K from 10-100 IRE, and had
the best overall dE performance.
Color Accuracy
All of the primary and complementary
color measurements in this section were
made after setting the white reference to
D65 at 75 IRE, but without calibrating the
individual colors with a color analyzer.
In the “Standard” Color Adjustment
mode, the DPX-1100 native primary colors
extend beyond the Rec. 601 and Rec. 709
primaries. This produces extremely vivid
colors, but reds and greens appear oversat-
urated, particularly with standard-definition
sources. The first CIE diagram shows that
the native green and red primaries lie well
outside the Rec. 709 high-definition primaries.
The WRGB and WRGBCYM modes are
f a c t o ry preset to the Rec. 709 high-definition
primaries. The second CIE diagram was
produced with 720p digital RGB signals. It
shows an excellent match, with the Rec. 709
HDTV standard colors without any additional
calibration with a color analyzer. Measure m e n t s
with 720p digital YCbCr signals produce
the same CIE (x,y) values within 0.001,
which indicates that there is negligible error
in the high-definition YCbCr/ YPbPr color
decoder. I also repeated the measurements
with analog 720p YPbPr signals, and again
all of the CIE (x,y) values agreed within
0.001. This is superb performance that indi-
cates that the analog A/D converters are
precisely calibrated to produce negligible
error in the analog video signal path.
Next, I manually entered the Rec. 601
primary and complementary color coordi-
nates into the WRGBCYM settings. The third
CIE diagram was produced with 480p digi-
tal YCbCr signals. It shows an excellent
match with the Rec. 601 standard-definition
colors. The same measurements taken with
480p digital RGB signals exactly re p ro d u c e d
the same effective primary colors, and the
largest deviation in a complementary color
was only 0.003. Each color can be individu-
ally calibrated with a color analyzer, but the
visual differences in the image were nearly
insignificant.
Scaling And Overscan
The DPX-1100 includes a new feature
that gives the user a choice of two overscan
modes. In the Standard mode, I measured
about 2.5 to 4 percent overscan on each
edge of the frame, for each of the analog
and digital signal formats. The overscan
measurements below are for the Full mode,
which is intended to produce frames with
no overscan.
Except for some blanking along the
edges of the frame, the DPX-1100 produces
a spatially ‘pixel perfect’ image when its
HDMI input is driven by 720p digital video
signals. When the Sharpness control is off,
each visible pixel from the source is pre-
cisely mapped to a single projector pixel,
without scaling or edge enhancement.
There is no edge outlining on horizontal or
vertical lines, which are displayed with pre-
cisely the pixel widths or thickness pro-
duced by the source. The single pixel verti-
cal lines within the high frequency multi-
burst pattern are rendered as single pixel
lines with full contrast. However, there are
two blank pixel columns (vertical lines) on
both the left and right sides of the screen
and four blank pixel rows (horizontal lines)
at the bottom of the screen. There are no
horizontal or vertical position adjustments
for HDMI (or DVI) signals to make the blank
pixels visible.
The scaling was exceptional for 480i,
480p, and 1080i signals. With the AccuPel
generator set to produce video-edge transi-
tion rates, there was no visible edge outlin-
ing around 1080i vertical lines, and outlining
around 480i and 480p vertical lines was so
faint that it could barely be detected when
standing within a few feet of the screen.
There was only about one pixel of outlining
above and below 1080i horizontal edges
and only two pixels for 480i and 480p hori-
zontal edges. Digital video signals from set-
top boxes or DVD players will be similarly
transition-rate limited for movies or other
broadcast video sources. With faster PC-
edge transitions (analog or digital signals)
equipment Review
Widescreen Review • Issue 88 • September 2004 5 Page 5/7