the new wave of LCDs
Understand the Technology
What’s important? What’s hype? What do those numbers on the box mean?
We’re glad you asked
COLOR GAMUT
The human eye can perceive a far more ex-
pansive range of colors than a computer or
television display can produce. The subset
of colors a display is capable of producing
is defined as its color gamut. Typically, a
display’s gamut is measured as a percentage
of the National Television System Commit-
tee (NTSC) color standard, with 72 percent
of that range being standard for LCDs.
Recent technology advances, however, have
enabled displays to reach 92 percent and
even beyond 100 percent of the NTSC. But
the expanded range of colors can come at
the cost of color precision if a display’s color
depth hasn’t increased as well.COLOR DEPTH
An LCD’s color depth defines the number of
levels that each primary color can render.
In an 8-bit panel, the red, green, and blue
channels of a pixel are capable of 256 levels
each. Multiplied, that makes for a total of
16.7 million possible colors. (This numberdoesn’t change if the display’s color gamut
broadens; the space between colors only
widens, thereby diminishing color preci-
sion.) With 6-bit LCD panels, which are in-creasingly common, the red, green, and blue
subpixels of a single pixel are capable of just
64 levels each for a total of 262,144 colors.
That’s a big drop from their 8-bit counter-
parts. To compensate for the difference,
manufacturers use techniques such as dith-
ering and frame-rate control on 6-bit panels
to expand their palettes. Traditionally, these
techniques have been able to elicit up to
16.2 million colors, but it’s now common
for 6-bit panels to claim 16.7 million colors,
making it difficult for consumers to discern
whether a display is actually an 8- or 6-bit
panel. See the sidebar on this page for more
on this issue.BACKLIGHT
The vast majority of desktop LCD moni-
tors have backlights made of cold-cathode
fluorescent lamps (CCFL), but the use of
LEDs for backlights is rising. LED backlights
use a grid of either white or mixed red,
blue, and green LEDs to create the display’s
backlight. In the latter case, the panel’s color
is theoretically improved because the back-44 | MAXIMUMPC | OCT 08 | http://www.maximumpc.com
Know Your Panel’s Lineage
While all modern LCD monitors fall under the thin-film-
transistor (TFT) classification, subsets within that class
bear notable differences. These are the most common
types of TFTs:
> TN (Twisted Nematic): The most inexpensive and com-
monly used TFT, TN panels are known for having extremely
fast pixel response times and a 6-bit color depth. These
panels feature inferior viewing angles and lower color
fi delity than S-IPS or S-PVA panels.
> S-IPS (Super In-Plan Switching): Considered to be the
best overall TFT in terms of color reproduction and viewingangle, S-IPS panels are often sold at premium prices, so
they’re sold by a limited number of manufacturers. The pan-
els have 8-bit color depth, although black and dark grays
can take on a purplish hue at wide viewing angles. And the
overdrive technology manufacturers use to elicit faster
pixel response times from these panels can introduce noise
into videos, unless your monitor or videocard comes with a
built-in noise-reduction function.
> S-PVA (Super Patterned- ITO Vertical Alignment): S-PVA
panels also have 8-bit color depth and better color repro-
duction and viewing angles than TN panels. S-PVA panels
feature better contrast and black levels than both TN and
S-IPS panels, and S-PVA is usually the panel type found in
higher-quality (but not professional) monitors.TFT COMPARISONBUYERS GUIDEThe triangle in the center of this chromacity
diagram represents the NTSC color gamut,
used to measure the color output of LCDs.