Video Hardware - Upgrading and Repairing PCs - page 659

Note
The 1080i HDTV standard is an interlaced mode that is sometimes used because it requires
half the bandwidth of the 1080p (progressive) mode. However, in most cases, you will not see
a DLP, LCD, or plasma TV flicker when it receives a 1080i signal. That is because the signal
is normally converted internally into a progressive signal and scaled to the display's native
resolution.
Image Brightness and Contrast
Although it's a consideration that applies to both LCDs and CRTs, the brightness of a display is
especially important in an LCD panel because brightness can vary a great deal from one model to
another. Brightness for LCD panels is measured in candelas per square meter (cd/m2), which is also
called a nit (from the Latin nitere , “to shine”) and often abbreviated as nt . Typical ratings for good
display panels are between 200 and 450 nits—the brighter the better.
Contrast is normally expressed as the ratio between white and black, with higher ratios being better.
There are unfortunately different ways to make the measurement, but the one that is most important is
the static contrast ratio , which is the ratio from brightest to darkest that can be produced on a display
simultaneously. Many display manufacturers like to quote dynamic contrast ratios instead because
they are measured over time with different backlight brightness settings and produce significantly
larger numbers. For example, a display with a 1000:1 static contrast ratio can also have an 8000:1
(or higher) dynamic contrast ratio. Even more confusion comes from the fact that many display
manufacturers like to assign their own proprietary names to dynamic contrast ratios—for example,
Acer calls it ACM (Adaptive Contrast Management), whereas ASUS calls it ASCR (ASUS Smart
Contrast Ratio). I recommend comparing displays using only the static ratio.
Typical static contrast ratio values range from 400:1 to 1500:1. Anything higher than that is generally
a dynamic ratio. Because of the capabilities of the human eye, static ratios over 1000:1 offer little
perceptible visual difference. A good combination of both brightness and contrast is a brightness
rating of 300 nits (or more) along with a static contrast ratio of 1000:1.
Note
When you evaluate an LCD/LED TV monitor, be sure to note the brightness settings available
in computer mode and TV mode. Many of these displays provide a brighter picture in TV mode
than in computer mode.
Display Power Management Signaling
Monitors, like virtually all power-consuming computer devices, have been designed to save energy
wherever and whenever possible. Virtually all monitors sold in recent years have earned the
Environmental Protection Agency's Energy Star logo by reducing their current draw down to 15 watts
(CRTs) or 5 watts (LCDs) or less when idle. Power-management features in the monitor, as well as
controls provided in the system BIOS and in the latest versions of Windows, help monitors and other
types of computing devices use less power.
For more information about power management, see Chapter 18 , “ Power Supplies , ” p. 845 .
Display Power-Management Signaling (DPMS) is a VESA specification that defines the signals a
computer sends to a monitor to indicate idle times. The OS normally decides when to send these