NEC MultiSync LCD2180WG-LED Reference Manual page 5

are possible due to the look-up-table being used
to compensate for the white point. Depending on
the display's native white point and the desired
white point, a significant number of display-
able colors may be lost leading to color banding
issues. This is especially true for displays that
do not feature programmable internal look-up-
tables with a depth of 10 bits or more.
LUT Input
Typical CCFL Display LUT
However with the LCD2180WG-LED display, the
white point is adjusted by directly varying the
brightness of the red, green and blue LEDs. This
means that the full range of the internal 10
bit look-up-tables is available for performing
response curve and gamma adjustments.
LUT Input
Typical LED Display LUT
10 Bit Look Up Tables
Since the LCD2180WG-LED has internal 10 bit Look Up
Tables (LUTs), that can be programmed by the calibration
software, the 8x8 bit LUT on the Host Computer can be
set to linear. This means that no steps are lost in an 8x8
LUT and subsequent 8 bit DVI bottleneck (assuming 10
bit DVI functionality is not used).
Also, since the white point of the display is controlled
directly by varying the intensity of the Red, Green and
Blue LEDs, the 10 bit LUTs in the display are only used
for gamma / tone response curve corrections. This pre-
serves the maximum number of discrete color levels.
On a traditional CCFL display monitor, the 8x8 LUT on the
host computer is used for both white point and gamma
/ tone response curve corrections. This means a loss in
the total number of discrete color levels which can lead
to color banding issues.
Additionally, with traditional LCD displays, the na-
tive white point of the backlight source is fixed,
and the white point is adjusted using look-up-
tables. Therefore, the greyscale color tracking
of the display is often poor, especially for very
dark colors. This is because for very dark colors
including black, no color corrections are possible
using the look-up-table. The color of black on the
screen will be the color of the backlight source
that leaks through the LCD panel, which may dif-
fer from the desired white point.
LED Backlight monitor
CCFL Backlight monitor
1 2 3 4 5 6
Delta-E
Typical Color Tracking
With the LED backlight, the white point of the
entire backlight source is changed by varying the
intensity of the red, green and blue LEDs. So the
color of absolute black on the screen will be much
closer to the intended white point. This provides
vastly improved greyscale color tracking.
HOST COMPUTER
8 bit x 3 colors 8 bit in x 8 bit out
Frame Buffer x 3 colors LUT
(Set to Linear)
HOST COMPUTER
8 bit x 3 colors 8 bit in x 8 bit out
Frame Buffer x 3 colors LUT

Another advantage of the LED Backlight is that
the contrast ratio of the display remains almost
constant as the white point is changed in inten-
sity and color. This is because the intensity and
color of black will also change due to the entire
backlight source being adjusted, rather than
having a fixed backlight and LUT adjustment with
a typical LCD display.
Gamut Mapping / Emulation
While the native color gamut of the display
exceeds that of even AdobeRGB, it is sometimes
necessary to preview images as they would be
seen on a display with a smaller colorspace.
The LCD2180WG-LED has presets for emulating
displays with both sRGB and AdobeRGB gamuts
by using internal color gamut mapping. These
presets can be selected with the touch of a but-
ton and will transform the displayed image into
either sRGB or AdobeRGB gamuts.
7 8 9 10
OmniColor Hue & Saturation Adjustment
LCD2180WG-LED DISPLAY MONITOR
8 bits in x 10 bits out
x 3 colors LUT
8 bit DVI
TYPICAL CCFL DISPLAY MONITOR
8 bits in x 8 bits out
x 3 colors LUT
8 bit DVI
LCD Panel
with LED Backlight
DDC/CI Adjustment
LCD Panel
with CCFL Backlight