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HOME REVIEWS CONTACT ABOUT March 14, 2009
HDTV for the Non-Geek
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The FCC standards for HDTV
broadcast becoming effective. The
amount of
information to be digested is intimidating, even for the
professional. The old hardware does not become obsolete,
but it
will require
a tuner to convert from the new signal, to the old signal.
If you
have cable TV, this will be taken care of by the cable company.
However,
this might be a good time to upgrade your hardware.
The new
standard offers a much better picture.
In the current
world of
digital projectors, LCD, LCOS, Plasma, and DLP are
the four
different kinds of televisions that dominate the HDTV
market. Each has unique advantages over the
other. Plasma
and some
of the LCD screens can be mounted on the wall, although
surveys
find that few people do mount them on the wall.
DLP
and LCOS
and some of the LCD units are both projector technologies.
Rear
projector units are usually the most cost-effective. The size
of some
systems is now less than 12 inches in depth.
Video
quality on the best projectors now surpasses that available
in a
conventional commercial movie theater. When reviewing
information
about the different techniques, pay attention to the
source of
the information (duh!). A manufacturer
of one
technology
will probably be biased in favor of that technique.
Different System Types:
Traditional TV:
also called direct view, has the images displayed on a picture tube (Cathode
Ray Tube). LCD (Liquid Crystal Display)
and Plasma TV can also be direct view.
The LCD and Plasma TV systems are the “flat-panel” units.
Rear Projection TV (RPTV): uses a combination of mirrors and lenses to project
the image from behind onto the viewing screen.
This enables the displayed picture to be significantly larger, up to 70
inches or more. This technique usually offers the best value (picture size vs.
cost).
Front Projection TV (FPTV): this is like a movie theater. The image is projected forward, to an
external screen. But like a movie theater, a very dark room is required because
the screen will reflect any light in the room.
This technique is usually more expensive than rear-projection, but the
footprint (the area consumed by the equipment) of the system is smaller.
TV Display Techniques:
CRT
(Cathode Ray Tube): Traditional TV Technology - The established standard for television
displays; good value, picture quality.
The maximum size of the screen is smaller with the technique. The technology is still a good choice where a
smaller picture is desired, and bulkiness is not a concern.
Liquid Crystal Display (LCD): Thin
design, but has problems displaying images in motion (sports), the images tend
to streak. These projectors usually
contain three separate LCD glass panels, one for red, green, and blue
components of the image being projected. As the non-colored light passes
through the LCD panels, individual picture elements (pixels) can be opened to
allow light to pass or closed to block the light. This produces the image that
is projected onto the screen.
Historically,
LCD sets have had a problem with visible pixelation (screendoor effect).
It looks like you are viewing the image through a screendoor. This is less apparent on newer sets with
higher screen resolutions.
Pros:
Ø
Better color
saturation, more rich and vibrant
Ø
Better sharper
image, important for text
Ø
More energy
efficient
Cons:
Ø
Poor black levels
and contrast
Ø
Problems
displaying images in motion (sports)
Ø
LCD panels (mainly
in the blue channel) can degrade, causing shifts in color balance.
Ø
Visible pixelation (screendoor
effect)
Liquid Crystal on Silicon (LCoS): A type of LCD
Technology, LCOS
uses liquid crystal rather than mirrors to project (usually rear projection) an
image on the screen. LCOS is a good value compared to plasma and LCD sets, but
expensive when compared to all other rear projection television technologies
such as DLP. This technique uses a chip
like a DLP (see below) set does, but the chip is coated with liquid crystal,
which reflects the image seen on the screen.
LCOS based systems allow for higher screen resolution than an LCD
display or a plasma display.
Pros
Ø
Sharp, vivid
colors, and deep black levels
Ø
It does not
slowly change over time as a plasma set does
Cons
Ø
Dead pixels
usually happen because the technology is partially reflective.
Ø
High Maintenance
Cost: LCoS
requires frequent bulb changing requirements (anywhere from 6,000 to 8,000 hours,
about 3-4 years with normal usage) versus 50,000 or more for most LCD or plasma
screens. A replacement bulb will cost
about $400.
Ø
Reproducibility:
Image quality can vary greatly from machine to machine.
Digital Light Processor (DLP): The DLP is a Texas Instruments product that is
manufactured in
In the best
DLP projectors, like the ones in use at your local movie theater, there are
three separate mirror chips, one each for the red, green, and blue channels.
However, in the DLP projectors marketed for the masses, there is only one chip.
In these sets, to define color, there is a color wheel that consists of red,
green, blue filters. This wheel spins between the lamp and the DLP chip and
alternates the color of the light hitting the chip.
The
spinning color wheel used to project the image can produce a problem on the
screen known as the rainbow effect, which is colors separating out in distinct
red, green, and blue. At any given point
of time, the image on the screen is either red, or green, or blue, and the
technique relies upon your eyes not being able to detect the rapid changes from
one to the other. However, not only can some people see the colors separate,
but the rapid sequencing of color may be responsible for reported cases of eye
strain and headaches. But the vast
majority of the people cannot detect the rainbow effect.
Newer
sets have the color wheel rotation speed doubled. Also, newer sets utilize a
six-segment color wheel (instead of a 3 segment) that has two sequences of red,
green, and blue. Because the wheel is at double speed, and because the red,
green, and blue are seen twice in every rotation, the effect is a quadrupling
of the rotation speed. This eliminated the visibility of rainbows for most of
the people who previously saw the effect.
Mitsubishi
recently introduced LaserVue, a DLP set that uses a
laser instead of the conventional lamps.
The design also eliminates the need for the color wheel.
Pros:
Ø
Small package
size
Ø
High contrast
image with deep black levels
Ø
Good value
Cons:
Ø
Less bright
images
Ø
Rainbow effect
Ø
High Maintenance
Cost: DLP requires frequent bulb changing requirements (anywhere from 6,000 to 8,000 hours,
about 3-4 years with normal usage) versus 50,000 or more for most LCD or plasma
screens. A replacement bulb will cost
about $300-$400. Samsung is using LED
illumination instead of lamps. The LED
should not have to be replaced.
Plasma
Display: Thin design,
high contrast ratings, Size up to 60 inches or more; some display
limitations: costly, older systems had a
high burn-in risk (over time, a memory of what was projected was retained);
This could pose a problem for those who like to play video games or watch taped
movies. If you put the game or tape on pause for too long, this could burn an
image into your screen.
Pros:
Ø
Exceptional
picture quality: It can produce up to 8.6 billion colors, an accurate color
reproduction and wide viewing angles.
Ø
Large screen
sizes: Some Plasma TV units are now manufactured in screen sizes that can span
up to 100 inches.
Ø
Lifetime: Plasma TVs
are also known for their extended lifespan capacity of approximately 60,000
hours and great contrast (deep blacks).
Ø
Less Expensive
than LCD
Cons:
Ø
The displays are
very bulky, heavy, and fragile.
Ø
Burn-in
Ø
Slowly degrades
over time
Ø
Energy
inefficient
|
|
Plasma |
LCD |
LCD |
LCoS |
DLP |
|
Display
Type |
Direst
view |
Direct
View |
Projection |
Projection |
Projection |
|
Brightness |
Good |
Excellent |
Good |
Good |
Good |
|
Black
Level |
Excellent |
Fair |
Fair |
Excellent |
Good |
|
Contrast |
Excellent |
Fair |
Fair |
Good |
Good |
|
Motion
(Sports) |
Excellent |
Good |
Good |
Excellent |
Excellent |
|
Viewing
Angle |
Excellent |
Good |
Good |
Good |
Good |
|
Aging |
Good |
Good |
Good |
Excellent |
Excellent |
|
Cost
of Owner-ship |
Good |
Excellent |
Fair |
Fair |
Fair |
Standards:
NTSC
Analog TV or Standard Definition TV (SDTV):
The current system that is being phased out (National Television Systems
Committee).
EDTV (Enhanced
Digital TV): basically high-end Standard Definition TV. While these sets may be
better than standard sets, the picture quality is not equal to HDTV.
Technically, there is little difference between an SDTV and an EDTV (except for
the higher price).
ATSC
Digital TV: This is the new system (Advanced Television Systems Committee),
which by the way; is not necessarily
.
HDTV: is digital TV where the image is a
wide-screen picture with many times much detail than is contained in current
analog television pictures. Most consumers will see a
huge improvement in image quality. HDTV
has a better quality image than SDTV because it has a greater number of lines
of resolution. The image is two to five times sharper because the gaps between
the scan lines are narrower.
Summary
Any of
the four technologies can be a good choice.
The
competition is intense, and all of the technologies will continue to
improve. Buying a TV will never again be
as simple as it was before HDTV, but the benefits are worth the headaches.