What is a CRT?
CRT is an acronym
for cathode-ray tube. It is most familiar to us as what we call a picture
tube in our television sets. A standard television set uses one CRT
with a special mask inside that allows for small dots or lines of the
colors red, green and blue to make up a color image. A 3-tube or 3-CRT
projector uses 3 separate CRTs, one for each color. A basic CRT is comprised
of a cathode-ray in the neck of the tube and a phosphor
coated glass at the front of the tube. The cathode-ray shoots a beam
of electrons which strikes the phosphors on the front glass causing
them to emit visible light.
What is an LCD panel?
LCD is an acronym
for Liquid Crystal Display. An LCD panel is a translucent glass panel
that shows a computer or video image using a matrix of tiny liquid crystal
displays, each creating one pixel ("picture element," or dot)
that makes up the image. The first LCD panels were used with an overhead
projector for a light source, but today the term generally refers to
the smaller panels used internally in today's LCD video projectors.
What is an LCD projector?
A self-contained unit that combines three LCD
(Liquid Crystal Display) panels and a high intensity light source
for a complete computer and/or video projection device. LCD
projectors come in a wide variety of sizes and specifications,
so it can be very helpful to have the experts and United Visual
help you make the right choice for your application. The basic
design of an LCD projector consists of a light source, a prism
to split light into Red, Green and Blue which is then passed
through the transluscent LCD panels, combined and focused via
optics onto a projection screen. LCD offers huge advantages
over older CRT based projectors in brightness, size and weight.
What type of care and cleaning do LCD projectors require?
The requirements vary from vendor to vendor, but
we can provide a general rule of thumb to cover nearly all cases.
First of all, use the same care you would with any electronic
equipment; avoid exposure to extreme temperatures and impacts.
But beyond common sense care, you must develop a filter cleaning
regimen to greatly extend the life of your LCD projector and
those costly lamps. All LCD projectors have one or more sponge
or cloth intake filters. As a general rule of thumb, these filters
must be cleaned or replaced after every 100-300 hours
of projector use. Sponge filters can usually be blown out with
canned air or run under water and then allowed to dry before
re-installing. Failure to follow this regular procedure will
likely cost you hundreds of dollars in repairs when the projector
is 3-4 years old. In many cases, the LCD panels themselves will
be damaged by overheating and the projector will be beyond economical
repair. In addition, LCD projectors used regularly should be
professionally cleaned internally at least every 2 years. This
will remove the pesky dust particles that show on, or tint the
projected image and more importantly clean out the built up
dust and dirt that prevents good airflow to cool the lamp and
electronic components. Lack of proper maintenance will cause
premature failure of the lamp power supply (ballast) as well
as the LCD panels themselves. If you know anyone that has needed
these repairs, you'll understand why you want to avoid them!
What is a DLP projector?
A self-contained projector alternative to LCD
technology using Texas Instruments DLP technology. DLP
(Digital Light Processing™) typcially uses a single self-contained
digital display chip, actually called a Digital Micromirror
Device (DMD). The device contains millions of microscopic tilting
mirrors that are tilted to either reflect light, or not, depending
on the video signal. This complex, but ingenious device, actually
only produces images in black and white, but a high speed rotating
color wheel is introduced into the light path to transform the
image into color. In contrast to LCD, the light does not pass
through the DMD device, it is reflected by all these tiny mirrors.
DLP projectors offer the same advantages over CRT as does LCD
projection, while allowing lower power lamps to provide brighter,
higher contrast images, but also introduces a mechanical device,
the color wheel motor.
Is it true that, unlike LCD, DLP projectors don't need cleaning?
NO! This is the little white lie that DLP
vendors tend to use by misinterpreting the actual advantage
DLP has over LCD. While it is true that most, if not all, DLP
projectors do not have intake dust filters, that doesn't automatically
mean they will stay pristinely clean forever. The true reason
for removing the filters is to prevent typical human nature
from allowing DLP projectors to clog up, overheat and fail,
just like LCD projectors do when the filters aren't cleaned.
You can't get away with removing the filter on an LCD projector
because little speckles of dust will end up on the panels and
eventually obliterate the projected image. With DLP, it is rare
that dust can settle on the one tiny DMD chip, which has a color
wheel rotating and high speed in close proximity, in effect
acting like a fan to blow away the dust before it settles. So
in this respect, it's true that part of the projector doesn't
need regular cleaning; the DMD chip and the dust filter that
doesn't exist. However, because there is nothing filtering the
airflow through the projector, which is still needed to cool
the extremely hot lamp and the electronics it is baking, the
annual or semi-annual cleaning by a professional is even more
important. The fan(s) in a DLP projector will collect dust and
be weighted down sooner than on an LCD and that makes the fan
run slower. The reduced cooling and dust that is sucked into
the projector cause the lamp power supply (ballast) to require
more regular cleaning or they will fail due to overheating even
sooner than in an LCD projector. Bottom line: DLP projectors
need annual or bi-annual cleaning just like LCD projectors.
What is a Plasma monitor?
Gas plasma technology is a new way to build flat
video and computer monitors. Essentially plasma units have the
brightness and look of a CRT monitor, but
they offer a much larger image and are thin enough and light
enough to hang on any wall. This combination makes them ideal
where lighting conditions would favor a monitor, but audience
size indicates a projector. Like LCD displays, plasma monitors
do not exhibit the distortion and loss of clarity in the corners
inherent to CRTs. However, Plasma displays share the problem
of all phosper based displays; burn-in. Be aware that Plasma
displays are not a good choice when portions of the image do
not regularly change, such as a running information bar at the
bottom of a news station. Image burn will occur fairly quickly
in these situations. Click here
for more details about how a plasma monitor works.
image, courtesy of Fujitsu General America, Inc.
Phosphors are the material
that emit the visible light that makes up the picture we see from
a standard CRT
based television, projector, computer monitor or the new plasma displays.
In a CRT the phosphors are on the inside of the front glass and are
excited by a beam of light from the cathode-ray. In a gas plasma flat
display, the phosphors are on the inside of the rear glass of the
millions of tiny cells or bubbles. The phosphors are excited by UV
light produced by electromagnetically charged plasma in the cell.
is an ANSI lumen?
An ANSI lumen is a measure
of brightness put out by a projection device, as standardized by the
American National Standards Institute. Note these are not comparable
to "lumens" expressed in non-ANSI terms (and used to measure,
for example, the output of overhead projectors).
How many ANSI lumens do I need to get a good image?
depends on your room lighting conditions and screen size. As a rough
guide, a rating of 150 to 300 ANSI
lumens (the brightness of three-tube CRT projectors) is
adequate with a 60" diagonal screen with room lights off, but
you should look for something in the 700 - 800 range for a 100"
to 150" screen with lights dimmed, and at least 1200 ANSI lumens
when you go to a 300" screen or want to project in bright lighting
conditions. Your best bet, of course, is to ask your sales rep to
demo the projector under conditions typical to what youll see.
What is peak lamp life?
Most LCD projectors use
a metal halide source, which offers a very white light and a life
of 750 - 4,000 hours or more. They typically do not burn out, but
gradually grow dimmer, giving you plenty of warning that its
time for a replacement. With this type of lamp,
total lamp life is not a very useful measurement, as the lamp will
continue to function long after they're so dim you won't want to use
them. So manufacturers' offer a peak ratingand peak lamp life
is the time the lamp will last at 80 - 90% of total brightness.
What is resolution?
The resolution of your
computer display measures the amount of detail that can be seen in
an image, expressed as the number of distinct horizontal and vertical
lines visible on a test pattern.
are VGA , SVGA, XGA, SXGA and UXGA?
VGA in an acronym for Video
Graphics Array. VGA, SVGA and XGA all measure the resolution of the
video signal being output by a personal computer. VGA consists of
640 vertical lines x 480 horizontal lines, SVGA 800 lines x 600 lines,
XGA 1024 x 768, SXGA 1280 x 1024, and UXGA 1600 x 1200.
is horizontal and vertical resolution?
A video or computer image
is made up of rows of horizontal and vertical pixels. Its resolution
is limited by the number of distinguishable rows, or lines, that the
monitor or LCD device can form. "Horizontal resolution"
or, more properly, "horizontal lines" is the number of distinct
lines that you can count going across the image--but if you look at
your monitor, these lines would actually go up and down, or vertically.
"Vertical resolution" measures the number of distinguishable
lines you can count from top to bottom in the image.
In computer projection,
the number of lines is only limited by the signal coming out of the
computer and the quality of the projection device. In
television, the number of vertical lines of resolution is fixed: the
American, or NTSC, standard is 525 vertical lines. The number of horizontal
lines will vary with the quality of the monitor or projector used,
but is still limited to less than 400 by NTSC standards. This limit
is one of the barriers that is broken with the introduction of Digital
What's the difference between VHS and S-VHS?
S-VHS was introduced in
response to the criticism of the poor video quality of standard VHS
recordings. S-VHS is not just a buzzword, but an entirely different
system of recording video signals on VHS size tapes. However, it has
never become a widely accepted format for consumers so it is a subject
S-VHS records luminance
and chrominance (b&w picture and color information, also called Y
and C) separately, rather than as a composite signal. By doing this,
the deck is able to record and playback a wider bandwidth, or a much
signal than a normal VHS deck. The signal is also output via a special
connector that also keeps the Y and C signals separate. The result
is a much clearer, higher definition picture than VHS can produce.
resolution of S-VHS is around 400 lines, compared to 240
lines of normal VHS in SP mode.
S-VHS is most often used
commercially or by educational institutions where they can record
video with an S-VHS camcorder at 400 lines and then edit it on S-VHS
editing equipment. This allows editing to be done with a very good
signal so that even after multiple copies are made during the process,
the final result is still higher than the quality of broadcast television.
If standard VHS was used, the end result would be noticeably poor,
even to an untrained eye.
Unfortunately, S-VHS rarely
finds its way into homes because you won't find movies to rent in
S-VHS. Also, if you make your own recording on the required special
S-VHS tapes, most standard VHS VCRs won't play them.
What is an s-video connector?
connectors are used for a variety of high resolution signals. It was
originally developed for use with S-VHS
recorders, but is now the standard for DVD players and is also used
for converting computer signals to video via a scan
converter. The connector has four connections (see diagram),
compared with two for a standard video connector. This allows the
luminance and chrominance (b&w picture and color, also called
Y and C) information to be transmitted separately allowing for a much
wider bandwidth and less crosstalk. The wider bandwidth translates
to a horizontal
resolution of about 400 lines compared with the normal
240 to 320 lines with conventional composite video connectors. Less
crosstalk means there will be less "snow" or "color
noise" in the picture. For reference, the S-Video connector's
pin outs are as follows: Pin 1 - Y ground, Pin 2 - C ground, Pin 3
- Y signal in/out, Pin 4 - C signal in/out.
What are DTV and HDTV?
DTV, Digital Television,
is a new broadcast standard that will provide vastly improved picture
and sound quality when compared to the current NTSC broadcast standard
in the United States. With DTV, viewers can see images up to six times
of their current TV’s. HDTV, High Definition Television, is one of
the possible formats that will be transmitted when DTV becomes available.
HDTV broadcasts are at the top end of the DTV spectrum. These broadcasts
will have the best sound quality, the ability to broadcast in a wide
screen format using a 16:9 aspect
ratio, and the best picture quality. For more details,
see our Tech Tip, DTV:Seeing
is believing provided courtesy of Sharp Electronics.
Should I hold off buying a TV until I can get a new DTV?
No. The FCC will continue
to offer analog broadcast space for television programming at least
until the year 2006, and broadcasters will simulcast
all broadcasts at least that long. Many experts believe that, due
to government rules that must be met before discontinuing analog broadcasts,
they will continue well beyond the target year of 2006. This means
the TV you buy today will probably be receiving broadcasts for the
next 10 years or more, and the life expectancy of a television is
only around 8 years. Coupled with the fact that early DTV sets are
very expensive, and that you will be able to buy a digital down-converter
for any current set, it doesn't make much sense to hold of television
purchases just yet.
What is a simulcasting in regards to DTV?
The simultaneous broadcasting
of the same program on analog and digital channels. This will enable
your analog TVs to continue to receive the same programs as shown
on the digital broadcast, without the need for a DTV down converter
What is a "component input" on monitors, TVs and projectors?
A component input is the preferred connector used with progressive
scan DVD players, digital HDTV tuners and digital VCRs. It works
by dividing the chrominance signal into red, green and blue
components and a separate luminance component similar to S-Video
but even more like a computer RGB data signal.Though
the new digital systems also have standard composite outputs,
connecting with the component input will improve picture quality
with higher resolutions than possible with composite or even
S-video connections as well as reduce noise by minimizing crosstalk
within the video signal.
Q. Can videotapes recorded
in the United States be used overseas?
Generally no. The reverse
is true as well: videotapes recorded overseas cannot be used in the
United States, except on specialized equipment.
The United States uses
a television standard called NTSC (for "National Television System
Committee"), which is not a worldwide standard. Historically, the
problem with NTSC was twofold. First, electric current in the U.S.
is 60 cycles per second, which provided engineers a simple timing
reference, so it was very natural to create a 30 frames-per-second
video standard here. In countries with 50-cycle current, NTSC did
not make sense. Second, most nations began broadcasting several years
after the United States and, by the time they did, several significant
improvements in image quality were possible. Not being committed to
NTSC-compatible equipment, they went with a better standard.
Today NTSC, which uses
525 lines per frame (and actually 59.95 fields-or interlaced half-frames-per
second) is used throughout North America, western South America, Japan
and several Asian nations. Most of western Europe, Australia, China,
India and many other Asian and South American nations use the PAL
standard (Phase Alternating Line, with 625 lines and 50 fields per
second). SECAM (Sequential Color with Memory, also 625 lines and 50
fields per second) is used in France, eastern and southeastern Europe,
the former USSR, plus most of southeast Asia, Brazil and eastern South
What you need to know is
that you have to match the tape format to the VCR and monitor that
will be playing the tape. Though many new monitors and TVs and nearly
all projectors will display any standard, most VCRs will not. Multi-standard
VCRs are available, but they're expensive and not commonly used (although
they are much more common in Europe and Asia than here). You'll want
to find out ahead of time which formats your overseas users can accept
and make sure you send a compatible tape. Most professional tape duplication
houses (including United Visual) can create cassettes in the appropriate
format by copying your NTSC (or PAL or SECAM) original.
What is an aspect ratio?
An aspect ratio refers
to the dimensions of a television screen or other screen. The ratio
refers to the width of the screen in relation to the height of the
screen. The aspect ratio of today's traditional TV is 4:3. For comparison,
the aspect ratio of a square screen would be expressed as 1:1 or 4:4.
The aspect ratio of HDTV
is 16:9. This is similar to the aspect ratio that many motion pictures
are shot in. The 16 refers to the width of the screen and the 9 refers
to the height of the screen.
Q. What is intelligent
Intelligent resizing, a
pixel mapping technique also known as "intelligent compression,"
"SizeWise," "Limesco," or a variety of other names,
uses a computer algorithm to map high resolution
computer images to a lower resolution LCD. Intelligent resizing works
much better than plain "compression," which most people
do not find acceptable. These algorithms work best going only one
step downusing an 800 x 600 projector you can get very good
pixel-mapped 1024 x 768 images. But you'll probably notice the drop
in quality when you input 1280 x 1024, especially on smaller text.
What is a video line doubler?
A video line doubler (or
scan doubler or scaler) increases the number of lines of vertical
resolution from 525 to 1,050 lines. Though it starts with a fixed,
525-line signal, the device uses a mathematical algorithm to create
525 more lines in between the lines coming from the signal. The result
is a much sharper image. Nearly all LCD projectors today include some
type of video scaler, since they must scale the 525-line image to
the native resolution of the projector.
What is a scan converter?
A scan converter is a device
that you connect between your computer and a regular television or
monitor to allow them to display computer signals. The idea sounds
good, but in reality when you convert a computer signal this way it
becomes very difficult, or impossible, to read text, although pictures
will look satisfactory. The reason for this becomes obvious if you
refer to the above articles on VGA
and vertical resolution. Even the best televisions or non-data
monitors are designed to NTSC standards which gives you a maximum
resolution of 400 x 525. VGA computer signals are 640 x 480 and the
higher resolution SVGA or XGA are fast becoming the standard making
the problem even worse. No matter what you do, you can’t clearly display
640, or more, lines of information on a monitor only capable of 400.
unless you are planning to display nothing but pictures, or very large
text, a scan converter probably won’t do what you hope it will.
Q. What is monitor loopthrough?
An output on the projector
or large-screen monitor that allows you to connect additional monitors
or projectors to display the same image.
A loopthrough output is
commonly used to run a desktop computer monitor at the same time the
computer image is being projected--thus allowing you to sit or stand
at the computer and always face your audience. Another way to accomplish
this goal is to supply a Y-cable with the projector, which allows
you to split the signal between your monitor and your large-screen
device. Note that this type of Y-cable must be designed specifically
for your projector by the manufacturer. Use of the wrong Y-cable with
computer signals can damage your equipment.
Generally, monitor loopthrough
is not helpful if you're using a laptop computer. The laptop's internal
circuitry must split the signal between the laptop's monitor and the
external device. Most laptops have such circuitry; some do not.
What is a Firewire?
Firewire, or IEEE1394, or Sony I-link, is a connection
that's being used to interface computers to digital video devices,
including digital camcorders and high-end digital still cameras.
It is very fast, up to 400Mbps, you can plug in after you have
started up your computer and you can daisy chain multiple devices.
The new USB 2.0 standard actually meets or exceeds this transfer
rate which somewhat limited the number of new computer products
using firewire. The downside of Firewire is that you can only
run about 5 meters with it. It consists of six wires: two for
power, two for data and two for synchronization. An advantage
of firewire is that most computers are able to control all the
camcorder functions (Play, FF, REW, Pause) via the firewire
cable making video editing directly from a digital camcorder
What is keystone correction?
Keystoning is when your
image appears wider at the top or bottom due the projector being positioned
somewhere other than the center of the screen. Keystone correction,
or lens shift, corrects this rectangular distortion. Most LCD projectors
today have a fixed keystone factor (allowing the projector to be placed
at about an 8-degree angle lower or higher than the center of the
screen), but many allow you to adjust keystoning. Thus you can place
the projector on your conference table, on carts of various heights,
or mount it on a ceiling of various heights without having to worry
about ending up with a distorted image.
What is a wireless mouse control on a projector?
A device that simulates
the operation of your computer's mouse from a wireless remote control,
generally the same control that operates your projector's other functions.
Why would I want a wireless mouse with my projector?
A wireless mouse unchains
you from your computer during presentations. Even if you find it difficult
to precisely control the mouse pointer, you'll find it invaluable
when using presentation software such as PowerPoint® or Astound®.
Just having the ability to click the mouse buttons to advance or reverse
the slides in a presentation make it a must have item
for presenters. Note: If you have problems using the mouse to go backward
in newer versions of MS PowerPoint®, see the Tech
Tip on this problem.