| Video Noise February 2007
Flat-Panel Displays: The State of the Art, Winter
2007
This month, I examine the two types of flat-panel video
displays from a realistic perspective -- that is, not from the perspective of some
salesperson or enthusiastic neighbor. When you take home that new LCD or plasma flat
panel, what can you expect from it?
Flat-panel torture test: shadows and black levels
LCD and plasma flat-panel displays excel at producing
bright, colorful images, even in rooms with a fair amount of ambient light. LCDs compress
blacks more noticeably than do good plasma displays, but neither is as good as a CRT or
the newer DLP and LCoS displays (HD-ILA and SXRD). Of course, CRT, DLP, and LCoS displays
aren’t flat panels. User adjustments on flat panels often can improve the black level
and shadow detail, but won’t completely stop the loss of detail when images get dark.
A technician trained by the Imaging Science Foundation (ISF) can use expensive calibration
hardware and a display’s built-in service menus to improve overall performance,
including shadows and black level. But even with a professional calibration, there are
limits to current LCD technology; the limitations of plasmas, on the other hand, may be
small enough to be ignored by some owners.
LCD panels have a backlight. In some sets, the
backlight’s level is adjustable. Experiment and see what you come up with.
You’ll need to readjust the Picture/Contrast and Brightness controls to get the most
out of backlight level adjustments. Being able to adjust the backlight will help, but it
won’t solve LCDs’ limited shadow detail compared to other display technologies.
Burn-in still an issue?
Plasma displays used to be criticized for their tendency to
permanently burn into their screens static images, such as channel logos or game graphics.
I still wouldn’t pick a plasma display for lots of gaming use, but other burn-in
problems, such as channel logos, have been eliminated in the last few years. For many
buyers, eliminating the risk of burn-in removes their main objection to plasma displays.
But remember -- once something is burned into a plasma screen, it can’t be removed.
Some makers of plasma sets may try to remove burned-in images by having them display lots
of bright image content, but this prematurely ages the screen -- not much of a fix.
LCD panels may, under severe operating conditions, appear
to have a burn-in problem, but this will disappear over time as other image content is
displayed over the burned-in logo or graphic. LCD flat panels thus make a pretty good
choice for a display that will see a lot of gaming use.
Need a heater in your TV room?
Plasma displays put out a lot of heat -- enough to surprise
people the first time they get close to a screen while it’s operating. LCD displays
produce a lot less heat, but they aren’t as cool in operation as you might have
expected modern digital hardware to be.
Motion makes artifacts?
LCD flat panels will have more visible motion artifacts
than their plasma counterparts. You might notice this in such things as nodding heads, or
scenes in which the camera is constantly moving. Newer LCDs are better, but are still not
plasmas’ equal in this regard. Also, the video processing in both LCD and plasma
displays can be slow enough to cause visible motion artifacts. The more video processing
needed, the slower it will be, and the more likely the results will be visible: action
that looks unnaturally jerky, wobbly, uncoordinated, smeared, or blurred.
Color performance
Though few casual viewers will ever notice it, plasma
displays have the edge over LCDs in color accuracy. LCDs, by nature, miss the standard
color points for red, green, and blue by small amounts, while plasma displays are usually
very close to these colors’ ideal values. Both technologies can look spectacular when
reproducing colorful, brightly lit images. The differences in color rendition may be
detectible by experts, but rarely by those not trained to look for such things.
Conclusion
As of winter 2007, neither LCD nor plasma flat panels
provide reference-quality images. But both can be made relatively flat, and that has a lot
of sex appeal in the consumer-electronics market. If you want a flat-panel display, keep
your expectations within what these display technologies can actually deliver and you
won’t be disappointed. If you want reference-quality images, however,
you’ll need to give up the idea that you can get them from a flat panel, and instead
look for a 1080p DLP (especially three-chip DLPs, which are quite expensive) or LCoS
display. (JVC’s HD-ILA and Sony’s SXRD are the most common brandings of LCoS
technology.)
As of now, LCD flat panels have the greater number of
compromises and limitations, making their overall image quality somewhat inferior to that
of plasma displays. If you want a flat display with the best possible image, plasma should
be your choice (unless you’ll be displaying a lot of static graphics). LCDs are a
better choice for heavy gaming and computer graphics.
All of this is subject to change over time. If you’re
reading this article in 2009, the entire playing field of video displays may have tipped
upside down. For those reading this in 2007, however, last month’s column will tell
you about more things to be aware of when shopping for a display.
...Doug Blackburn
db@hometheatersound.com |
