LCD Technology
Video projectors have been
manufactured using LCD as their image producing
technology for more than 15 years now. They produce
replaced the early 3 gun RGB projectors which you see
from time to time. The LCD is much like the screen of a
laptop computer however much smaller and the projector
has 3 screens, one for each red, blue and green. The
light is passed through the three panels which is then
combined to form the projected image.
LCD projectors have some
minimums and the first of these
is pixelation, or what's known as the screen door
effect. This means that sometimes you can see the
individual pixels and it looks as though you are viewing
the image through a screendoor. The second is that LCD doesn't produce
absolute black, which means that contrast is limited to
a finite level. However, the advent of higher
resolution LCD projectors, in particular the HD-ready
projectors, which have a horizontal resolution of 768
pixels or greater have been able to reduce the pixelation
to quite acceptable levels. Recent improvements have
provided the newer LCD's the ability to produce high-contrast images
to make them suitable and cost-effective for home theatre
enthusiasts.
DLP Technology.
DLP is the newer technology and it has been
developed to improve the picture over LCD and in that DLP projectors tend to be smaller
and lighter, have better contrast, and don't suffer the
same pixelation problems as LCD projectors. There is one
problem involving the visual separation of colour and
rainbow effects that some users report with DLP projectors
although it appears in low cost models usually it
can
only be seen by a very small number
of people. DLP is short for digital
light projection and the technology has a
much improved range of capabilities than LCD. This wider
range allows for the lower cost projectors to have
higher light output and the more expensive projectors
have greater clarity, resolution and contrast than ever
before.
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Contrast
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| High Contrast
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Low Contrast
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A term defining how far the whitest
whites are from the blackest blacks. If the peak white
value is significantly different than the peak black
value the signal is said to have high contrast resulting
in well defined sharp colour's. The higher the better
basically. A contrast of 400:1 means that the blackest
black on the image will be 400 times darker than the
whitest white.
The contrast ratio is an important
point to consider should you be looking for a home
theatre projector or when you wish to project in a
darkened room. Brighter rooms cancel out much of the
contrast produced by the projector.
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Brightness
There are
many projectors available with many brightness levels,
projector brightness is measured in lumens instead of in
watts like your standard household lamp. To decide on what
lumens you will need the following list should help to
guide you through:
 | Home theatre projectors will
rarely exceed 1100 lumens brightness. When your
watching a movie you will most likely dim most of the
light from the room, so a bright projector is not only
unnecessary it will be overpowering in a dim room.
Home theatre projectors generally focus on colouring
and high contrast more to give the very best of
images.
| Presentations in a dim room
allows you to decide from projectors around the 1200-
1600 lumen brightness level. Presentations require
people to be able to read from charts sheets and other
small texts and therefore you will need a little more
brightness than in home theatre .
| Presentations in a
well lit room will
require from 1700 to 2400 lumens brightness. This will
ensure that the image is visible on the wall/screen in
most lit rooms. Just remember the larger the screen
and the brighter the room the brighter the projector
will have to be.
| Larger venues presentations with
a lit room/hall. In this situation the recommended
level is 2500 lumens and above. The larger the screen has to be and
the more light that comes in the brighter the
projector will have to be. |
| | |
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Noise
The noise rating of each projector is
also an important consideration. Basically every
projector has a very hot lamp providing the light for
the picture. The projector is equipped with fans that
are designed to cool the lamp and prolong it's life. The
fans will be quieter on Economic mode as you are
basically turning down the lamps output and therefore
the heat produced. Generally anything below 30 dB is
very quiet. Home theatre projectors in particular should
be quiet as you don't want to be sitting in suspense at
a quiet point in the movie and hear an overwhelming
buzzing.
When buying a portable projector
the noise level is generally higher; the fans will have
to be smaller and spin at a faster rate to provide the
same amount of cooling.
Projector noise ranges
from 25dB up to
40dB.
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Throw
Distance and Projection Size
Image Size: 40
- 300inches (measured as the diagonal of it's size)
Throw Distance: 1.5 - 10Metres
( from projector to screen distance)
All projectors have a lens to focus the
image. When moving the projector back from the
wall/screen you will need to make slight adjustments to
keep the image in focus (not blurring out). This
adjustment does have a limit. In the above
specifications you will only be able to focus the image
at a distance of 1.5 to 10Metres. Having your projector
closer or further away will result in a blurred image.
At those distances the minimum image size is 40inches
diagonal and the maximum is 300inches diagonal. The
precise specification will vary with each projector, it
is best to look into your required distance and size and
buy a projector to suit.
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Inputs
Many people do not really consider the
importance of having the right inputs. You should pick a
projector with the right connections for your
equipment.
The hierarchy of video quality:
| - Digital video - DVI, FireWire or
HDMI
| - Component video
| - S-video
| - Composite video |
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BNC
(R/G/B/H/V)
A professional level
connector used to
connect high bandwidth video coaxial
cables. BNC is also referred to as Bayonet Network
Connector |
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D-SUB 15 pin
Also called a D-connector, or a
D-type connector. A type of connector commonly
found on computers and data transmission devices,
including SCSI devices and computer monitors.
D-type connectors have a "D-shaped" angled
housing, and have 9-, 15-, and 25-pin
configurations |
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DVI
Digital Visual Interface. The DVI
port provides a pure digital video signal to a
digital flat-panel display or projector. Using a
digital signal for the entire path maintains the
image quality at the highest level, because the
signal is not degraded as a result of a
digital-to-analog conversion. There is a maximum cable length
of 11 metres for this standard. |
 |
RCA (Composite)
A consumer standard connection
method used to transmit analog audio and video
signals between devices. Commonly used on most
receivers, televisions, satellite receivers,
VCR's, game console systems and speakers.
|
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S-Video
Small multi pin connector that
carries separate brightness and color signals from
a source component like a DVD player or satellite
receiver to a TV set.
This standard results in a much
improved brightness and clarity of the picture
over the single pin RCA composite video
signal.
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USB
This connection on projectors is
used for two purposes:
1. Most commonly it is
used as a feedback connection to the computer or
laptop, allowing you to click next slide etc on
the wireless projector remote and control the
presentation.
2. In some cases it is used with
PC FREE presentation projectors allowing you to
plug a USB memory stick into the projector and it
can project with no PC straight through the
projector. |
 |
Stereo-mini jack.
Much like the headphone connection
on your walkman or ipod, the stereo mini jack is
used to transmit audio into the projector.
3.5mm stereo jack plug for audio
use.. |
 |
D-sub 9pin
(RS-232)
Most commonly it
is used as a feedback connection to the computer
or laptop, allowing you to click next slide etc on
the wireless projector remote and control the
presentation.
Is fitted to projectors to allow for wired remote
control from a wall panel switch or an automated
AV control device.
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PC Card
(PCMCIA)
Personal Computer Memory Card
International Association. PCMCIA is an
organization consisting of some 500 companies that
has developed a standard for small, credit
card-sized devices, called PC Cards. These cards
in projector can be used to make the projector
wireless, add a network port, or connect SD memory
cards through to allow PC FREE presentations.
(only in some projectors) |
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HDMI High-Definition
Multimedia Interface
USB-like connection that can
transmit both uncompressed digital audio and video
signals while simultaneously adhering to the
High-bandwidth Digital Content Protection (HDCP)
standard. Generally found on home video
cameras. |
 |
RJ-45 (LAN
Connection)
This connection on a projector allows you to connect to it
to a
computer network
to control the
functions of the projector via a built-in internet
home page. |
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Wireless WIFI
(802.11b/802.11g)
Some
projectors come equipped with wireless
connections. Allowing you to connect any PC and in
some cases every PC to the projector. (some
Panasonic's allow you to connect up to 16 PC's to
their projectors splitting up the
screen)
In some cases an upgrade module
will have to be connected or WiFi card through
PCMCIA. |
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Resolution
The number of
pixels a projector is capable of displaying. The
resolution is described in terms of width x height. The
most common resolutions are SVGA 800W x 600H & XGA
1024W x 768H. A higher resolution will result in a finer
image. A projector with an XGA resolution usualy costs
more and in some circumstances may not be required. When
the main use is going to be power point presentations
you can easily get away with an SVGA resolution allowing
you to save some money.
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Aspect
Ratio (standard/widescreen)
The standard
proportion in width to height for a projector is 4:3,
but some home theatre projectors have a wider format:
16:9 or 16:10, designed for viewing movies or HDTV in
wide screen format.
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Keystone
Projectors are a
mobile device which can be placed in different angle to
the projection surface. To compensate for the skewing of
the image many projectors come with a keystone
correction feature, allowing you to adjust the image
back into a square. The most common type of keystone is
vertical with some of the higher end projectors coming
with both vertical and horizontal.
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Lamp Life
A major concern of
many projector buyers is the lamp life. Projector lamps
are expensive items and while the differ from model to
model they generally range from $400-$700. The majority
of lamps last from 2000 hours to 3000 hours which means
that on normal mode they will last 2000 hours and on
economy mode (which switches the brightness down) it
will extend it's life to 3000 hours.
|
Some models offer a
long lamp life of 4000 and in some cases even 5000
hours lamp life, making them a very good buy in
the long run.
While 3000 hours may
not sound like much but even under fairly heavy
use it does tend to last quite a while:
e.g. A
3000 lamp used for 2 hours a day every day will
last you about 4 years. |
 | Extending Lamp Life
When installing
plug in bulbs, be sure the lamps are seated completely.
The tendency is to stop at the first sign of resistance.
Continue to apply force at the base of the lamp until
you are sure the lamp is secure.
Switching Projector Off
Always
switch off using the remote control and not by
disconnecting the power, the projector will invariably
go into a cool down mode where the image is turned off
and the fan accelerates to cool the lamp in a controlled
manner. The temperature of an operating lamp is many
1,000's of degrees. Disconnecting the power to the
projector prior to the above process causes the glass in
the lamp to cool unevenly and will result in a stress
fracture and early lamp failure.
Shock and Vibration
Lamp failure
can be due to mechanical shock. A hot lamp filament is
very fragile, you should always make sure that the unit
is turned off and the lamp is cool before moving the
unit.
Economy mode
If your projector is
equipped with a "high/low lamp" switch you can extend
your average lamp life by using the "low lamp" position
whenever possible.
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