Choosing between
a Plasma TV and an LCD Television
Plasma vs
LCD - a Comparative Guide (3)
Functional Considerations
In this final part of our plasma vs
LCD TV analysis, we discuss how choosing either technology
impacts the end functionality of a flat-screen television.
Plasma vs LCD: Functional Related Issues
Are there any major
differences between these two different flat-panel TV technologies when it
comes to issues like image retention, computer use, lifetime, bad-pixels, response
time, and power requirements?
We look at each of these aspects to
discover more how plasma televisions and LCD TVs differ - if at all - in these
respects
Screen Burn-In and
Image-Sticking
When it comes to comparing plasma vs LCD TV sets, screen burn-in is probably one of the most debated topics by those in favor
of LCD display technology.
Yet,
while many are aware of the susceptibility of plasmas to burn-in, few realize
that even LCD TVs have their own problems - they suffer from a phenomena
known as 'image sticking'.
Though image sticking and burn-in yields practically the same visual impact
on the display panel, yet these two phenomena are completely different in their
nature.
Burn-in
As with all phosphor-based
screens, plasma displays are prone to burn-in.
Screen burn-in is a form of image retention and occurs when an image is left for too long on
the screen. This results in a ghost of the image burned on the
screen.
Keeping the brightness and contrast levels down, especially during
the first 100 or 200 hours of use will help reduce the risk of burn-in.
While some brands of plasma TV sets are more prone than others
to burn-in, yet in general, plasma screens are more prone to
suffer permanent burn-in during their first 200 hours of use. The reason is that fresh phosphors burn more intensely as
they are ignited.
Burn-in is the result of a damaged pixel
whose phosphor has been prematurely aged, and therefore glows
less intensely than those of surrounding pixels.
The presence
of a static image for more than 30 minutes may be enough to cause
temporary burn-in. Temporary burn-in or image ghosting should not be cause for
alarm, as normally this will wash out after several hours of use. Some models
have built-in features to remove image ghosting once this occurs.
More pre-occupying with plasma displays is the prolonged presentation of
black or gray bars, say when viewing
a 4:3 picture in its original format on a wide-screen display. This may easily
lead to permanent burn-in. Once permanent burn-in
occurs, the damaged phosphors in a pixel cannot produce the same levels
of light as that of the surrounding pixels.
Recent improvements in
plasma display technology have certainly extended the time it takes to burn
in a plasma pixel cell. The use of improved phosphor material, and motion
adaptive/pixel orbiting anti burn-in technology has greatly reduced the
risk of burn-in. It has got so much better that in our opinion,
people with normal viewing habits have nothing to worry about, especially
after the first 200 hours of use.
Still, keeping brightness
and contrast levels close to the lower end of the scale would help reduce
any
potential burn-in risks, especially if the application calls for part of the
image on the screen to remain static during use.
In these circumstances,
an LCD TV may be a better choice since LCD technology is not prone to screen
'burn-in'. In other words, no premature aging of pixel cells occurs in an LCD
TV panel due to the prolonged presence of a static image.
Image Sticking:
Still, LCD displays do suffer
from image sticking - a from of image retention that yields somewhat similar
visual results to burn-in in plasma TVs. The main LCD advantage here is that unlike
burn-in, image sticking can often be reversed to a point of total invisibility.
Image sticking is an intrinsic
behavior of TFT LCD panels. It can occur when a static image remains displayed
on the screen for an extended period as a result of a parasitic charge
build-up within individual pixels. This 'retained pixel charge' will prevent the liquid crystals to return fully to their
'relaxed' state upon removal of the static image.
The result is a faint, visible,
retained image that remains on the screen even when the image is changed. The
intensity of image retention varies among different brands. It also depends on
several factors including operating temperature, image make-up, and time the static image remained
on. Similarly, the level of reversing this image sticking depends on the causes that
led to image retention on the LCD panel.
More information on image sticking, including ways to reverse it and how best to
avoid it, is available in our article: Image
Sticking in LCD Televisions.
Plasma vs LCD - Image Retention
ADVANTAGE:
LCD TVs enjoys a technological advantage;
they are not prone to burn-in, and image sticking in LCD TVs is often
completely reversible, but...
Burn-in
is no longer much of a concern as it used to be with plasma televisions up to
the recent past, especially for people with normal TV viewing requirements.
Similarly, image sticking with LCD TVs is unlikely to take place under normal
home entertainment use.
Computer Use
Both the closer pixel built-up structure of an LCD
referred to in our second part of this plasma vs LCD discussion, and the burn-in issue of plasma panels
just discussed above, help render LCD displays more suitable
for computer use.
In particular, the higher number of pixels per
square inch on an LCD panel makes LCD monitors especially good at displaying
large amounts of data with exceptional clarity and precision. It is also for
this same reason that LCD panels tend to perform better in applications like video gaming.
Plasma vs LCD - Computer Use ADVANTAGE:
LCD, partly, because of their non-susceptibility to
burn-in, and partly as a result of their ability to display detailed graphics
better.
Life-time
The rare gases
used in plasma display panels have a life and will fade gradually
over use. Earlier plasma displays had a quoted half-lifetime
of between 20,000hrs, following which the image brightness will
fall to half its original value. However, the latest generation of plasma
displays boosts a quoted lifetime of 60,000hrs. Similarly,
LCD displays have an expected quoted half-lifetime of between 50,000hrs
and 60,000hrs. It is true that quoted half-lifetime figures by manufacturers
tend to be somewhat inflated, but still, these figures contrast heavily with the typical 20,000hrs half-lifetime for direct-view CRT TV sets.
But what do these half-lifetime figures imply? Statistics
show that TVs in an average US household remain on for over 7.5hrs a day. Further
more, on average, a TV set is replaced every 7 years. Taking a conservative figure of 30,000 hours
half-lifetime for either technology, this works out to well over 10 years of
daily use before these flat-panel TV sets would need replacement.
It
is thus clear that lifetime is not an issue when it comes to comparing
plasma vs LCD display technology.
At the same time, keep in mind that there is no way to re-generate
the gases in a plasma display. Similarly, it is impossible to repair
any ‘dead’ pixels that may develop during use in an LCD panel. The only option in
these
circumstances will be to replace the display.
Plasma vs LCD - Lifetime ADVANTAGE:
This is a non-issue with either technology - rather it
is more dependent upon manufacturer quality.
Bad Pixels
Both plasma and LCD displays may suffer from bad pixels
- at times also referred to as 'stuck' or 'dead' pixels. In other words, both
technologies may develop defective pixels during the manufacturing process
even though in plasma display, bad pixels are rare.
The interesting thing here is that some manufactures are
moving towards a 'zero' bad pixel policy. This means that they will replace
your flat-panel TV within (typically) 6 months from the date of purchase, should
it develop even just one single bad pixel during this initial period of use.
However, the issue of bad pixels within the context of plasma
vs LCD mainly arises with LCD TVs. The reason is that even if on day one, you
have a perfect LCD display, the
switching transistors associated with the pixels and sub-pixels in an LCD
panel may still get faulty at some point later in use.
Plasma vs LCD - Bad Pixels ADVANTAGE:
Plasma - because even though some manufactures are
offering a zero bad pixel policy, yet LCD displays still have a higher
tendency (with respect to plasma panels), of developing bad pixels during use.
Response Time and Fast-moving Images
Response time of LCD HDTV sets is surely among the latest battlegrounds between
display manufactures. The present de facto standard appears to be the 8msec for
LCD panels, though some manufactures are quoting response figures as low as 6msec and
even 3msec!
This response time debate is one of those hot topics with those in favor of plasma
televisions when comparing plasma vs LCD TVs.
For a detailed discussion on this subject, we suggest that you look at
our article on LCD Response Time. However,
for those who would like to go for the short answer, we still say that:
As things stand today, when comparing the pixel
response times of plasma vs LCD TV sets, plasma TVs still have a slight edge in performance during fast action movies, sports and gaming
events.
Plasma vs LCD - Response Time ADVANTAGE:
Plasma - because even though LCD technology have
improved to the extent that this is becoming less of an issue, yet LCD
technology has still some way to go to achieve the same pixel response level as phosphor based
displays.
Power Requirements
This is one of those few clear-cut issues in this plasma vs LCD TV
analysis; the advantage here goes to LCD TV sets. LCD panels use a backlight to produce images
that require substantially less power to operate than the plasma 'cell-based' display
structure.
The use of a backlight in LCD panels contrasts heavily with plasmas, which do require substantial power
to light each pixel forming the display.
The actual power requirements in LCD
displays depend mainly on the technology used for the backlight. In general, power
requirements for LCD panels are typically 40% to 50% less than plasma displays
of the same screen size.
Worth taking note it is possible to drastically
reduce the power requirements of an LCD TV or a plasma television, by simply
applying the correct settings for the contrast and brightness levels.
An interesting distinction between plasma and
LCD technology is that plasma displays require more power when handling bright subjects.
On the other hand, LCD panels require more power when handling dark subjects. This in view
that for an LCD display to present a dark subject, more pixels will have to be
activated to block more of the backlight light output from reaching the display
surface.
Plasma vs LCD - Power Requirements Comparative
Analysis: The table below depicts the actual power requirements for the
selected same-size LCD TVs and plasma television
models:
Plasma vs LCD - Power Requirements ADVANTAGE:
LCD - because the use of a common
backlight source to produce the image proves to be a more efficient way than
lighting the individual cells forming a plasma display.
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Plasma vs LCD Comparative
Summary
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