| Video Noise September 2008
Save the Plasmas
 Some
pundits are predicting that all self-contained video displays will soon vanish except
LCDs, which will be joined over the next few years by increasing numbers of Organic LED
(OLED) displays. (An LED is "organic" when it’s made of carbon rather than
the conventional silicon.) Some brands are dropping their rear-projection LCoS/LCD and DLP
models, even though large screens using these technologies are less expensive than LCD or
plasma displays of the same size. There’s no glamour, apparently, in a 65" DLP
rear projector that’s just 18" deep, even if it’s a full third cheaper than
a 60" plasma, or less than half the cost of the bigger LCDs. It will be a sad day if,
during this trend toward LCDs, plasma displays disappear -- in the last few years, the
image quality of plasmas has significantly eclipsed that of LCDs, especially in a darkened
home theater.
LCDs are great for use in bright rooms, for gaming, and for
displaying photos and other still content. But some new LCDs are so bright that you
can’t dim them enough for comfortable viewing in a darkened room. LCDs also have
problems with resolution once the image starts to move. High-definition resolution
(1920x1080) can decrease by two-thirds or more, down to about 633x350, because LCD pixels
can’t respond fast enough. A lot of video content doesn’t have all that much
resolution during fast motion anyway (use Pause to see for yourself), but you don’t
need your display making the problem worse. Plasma displays retain most of their
resolution, typically dropping only about 10% for moving content. Plasmas are bright
enough for viewing in rooms that have some light control, but may fall short in
bright daylight. A plasma’s maximum brightness is limited by thermal and power-supply
constraints. If you display a white box that fills 10% of the screen, then switch to a
full screen of white, you’ll find that most plasmas will be only about half as bright
when displaying the full white screen. This isn’t usually noticeable with typical
video content, but hockey and skiing events, and other programming that throws a lot of
white or near-white on the screen, might not look all that bright in a room with bright
lights or daylight.
 On the other end of the scale,
very dark blacks are an extremely important part of a video display’s performance,
giving images more realism and "pop." CRT displays used to be the gold standard
for dark blacks, but Pioneer’s Kuro plasma displays and some of the darkest LCD
panels are finally challenging that standard. Plasma black levels are, on average,
considerably better than the black levels of most of the LCD displays sold through last
year. This year, a few LCD models have appeared with very dark blacks, but the different
technologies used to produce these high black levels bring along with them other problems,
and can’t yet be considered completely successful. Other brands of plasma displays
may not be as dark as the Pioneer Kuros, but their black levels are dark enough to not be
a constant distraction, or an obvious limitation of image quality.
Large plasma displays also tend to be less expensive than
large LCDs. For example, Samsung’s 58" top-of-the-line plasma costs about half
as much as Samsung’s 57" LCD. This makes picking a large plasma an easy choice:
you get a more satisfyingly theater-like experience at a lower price. The prices of
smaller screens tend to be closer together; a 46" LCD costs about the same as a
50" plasma.
Plasma panels are still afflicted with image retention
(IR), a temporary condition in which an image that was displayed on the screen creates an
afterimage that can remain onscreen for minutes or hours after the video signal has
stopped sending it to the screen. How long such an afterimage lasts depends on how long it
was on the screen in the first place -- anywhere from 30 seconds up to several hours.
While IR has yet to be banished entirely from plasmas, it’s no longer the prelude to
disaster that it was in the past -- you no longer hear stories about plasmas suffering
from screen burn, a severe case of IR in which the afterimage becomes permanent and never
disappears. Carelessness can still result in screen burn, but you have to seriously abuse
a plasma display to make it happen. IR is most obvious when the screen is black, but
severe cases can be visible with normal video content. IR does fade to invisibility over
time.
But if your primary interest is viewing hi-def movies in a
theater room, it’s hard to beat the better plasma panels for the best viewing
experience. The best plasma displays I’ve seen this year are the Kuro models from
Pioneer and Pioneer Elite, and Samsung’s PN-xxA550 and PN-xxA650. The Pioneers have
the best blacks money can buy. The black levels produced by Samsung’s plasmas
aren’t nearly as dark as the Pioneers, and straight out of the box, the Samsungs are
an average mixed bag. But the Samsungs’ array of adjustments is impressive -- after a
professional calibration, their performance can be just about perfect.
. . . Doug Blackburn
db@hometheatersound.com |
