Hardware Reference
In-Depth Information
drawn in two passes—with the odd lines first and the even lines second. Each pass takes
half the time of a full pass in noninterlaced mode.
Early high-resolution CRT monitors used interlacing to reach their maximum resolutions;
as with interlacing, the vertical and horizontal scan frequencies were cut in half. Unfor-
tunately, this usually introduces noticeable flicker into the display, so in most cases you
should avoid interlacing where possible. Fortunately, most modern monitors support non-
interlaced modes at all supported resolutions, thus avoiding the slow screen response and
potential flicker caused by interlacing.
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 dis-
play 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 ab-
breviatedas
nt
.Typicalratingsforgooddisplaypanelsarebetween200and450nits—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 ex-
ample, 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 man-
ufacturers like to assign their own proprietary names to dynamic contrast ratios—for ex-
ample,AcercallsitACM(AdaptiveContrastManagement),whereasASUScallsitASCR
(ASUS Smart Contrast Ratio). I recommend comparing displays using only the static ra-
tio.
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
