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A projector
is a device that integrates a light source, optics system,
electronics and display(s) for the purpose of projecting an
image from a computer or video device onto a wall or screen
for large image viewing. There are hundreds of products available
in the market and they are differentiated by their resolution,
performance and features.
Display
There are several different display types with different picture
quality and lens life; LCD, DLP and CRT are the most common.
Cathode Ray Tube (CRT):
CRT projectors deliver a high degree of illumination and can
project high-resolution video and data at up to workstation
frequencies. Computer resolution can be as high as 2,000 lines.
The disadvantageof CRT projectors is that they need to be
realigned for different types and brands of computer, so if
you bring your laptop to the lecture theatre it may not match
any of the pre-programmed options and a technician will need
to be called to set it up.
Digital Light Processing (DLP):
The commercial name for this technology from Texas Instruments
(TI): The technology inside is often referred to as either
"micro-mirrors", or DMD: It works this way: build
a few hundred thousand tiny mirrors, and line them up in 800
rows of 600 mirrors each. Now attach a hinge to each of those
480,000 mirrors. Attach each of those 480,000 hinges to its
own very tiny motor! Power each motor with electrostatic energy!
The motors tilt their mirrors up to 20 degrees at incredible
speeds. This allows the mirrors to modulate light from a lamp,
and send the "modulated signal" out through a lens,
on to a screen. The most amazing part of DLP micro mirrors,
is the scale of size. The 480,000 mirrors (actually 580,000
are used), hinges and motors are packed onto a "wafer"
a bit larger than your thumbnail.
Liquid Crystal Display (LCD):
LCD stands for liquid crystal display and comes in many forms,
sizes, and resolutions. Its primary purpose is to present
a digital image for viewing. A common use of LCDs is as a
display on a notebook computer. Polysilicon TFT LCD is a popular
LCD technology for the top of the line LCD projectors. Monochrome
Polysilicon LCDs are typically placed in each of the three
color light paths inside a projector, one each for Red, Green,
and Blue. This results in increased color saturation, with
contrast ratios above 200:1. Polysilicon technology is also
a bit faster than the Active Matrix TFT, for smooth video
and multimedia. |
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LCD,
DLP, LCOS Projector Buyer's Guide - Resolution
Key Projector Features and Considerations
Finding the right projector is
easier than you might imagine. There are hundreds of projectors
currently on the market, but you can use our Find Projectors
utility to locate the best solutions for your presenting needs
after answering four simple questions:
What Resolution
should it be?
Does Weight & Portability
matter
How Bright
should it be?
What is your Budget?
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Are you usually
on the road with only a bag or two in hand, or are you interested
in creating a full-featured conference room? The size of a
projector reflects your presentation plans. Projectors come
in a variety of weights and sizes, so you need to be able
to decide what's right for your specific needs:
| Description |
Weight |
Mobile/Stationary |
Differences |
| Portable |
under 7 lbs. |
Extremely mobile |
Optimized for weight |
| Desktop |
7-13 lbs. |
Somewhat mobile |
Increased features & brightness |
| Conference Room |
over 13 lbs. |
Stationary |
Increased inputs, interfaces, features and brightness |
| Large Venue |
18-50 lbs. |
Stationary |
The ultimate in all features, except for portability |
| Home Theater |
varies |
Somewhat mobile |
High performance for home theater use |
How Do I Gauge A Projector's Brightness?
A projector's light output is measured in units called ANSI
lumens. The more lumens, the brighter the image.
| Lumens Range |
Typical Application |
Room Lighting |
| Less than 1000 |
Small conference rooms and classrooms |
Dark or very dim |
| 1,000-2,000 |
Midsize conference rooms and classrooms |
Dim |
| 2,000-3,000 |
Large conference rooms and classrooms |
Dim or normal |
| More than 3,000 |
Large venues (boardrooms, auditoriums, theaters etc.) |
Normal |
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Resolution |
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The sharpness and clarity of the picture on the screen
is determined by a projector's resolution. Resolution
refers to the sharpness of the image projected, as expressed
in pixels (the higher, the better). When it comes to
projectors however, the thing you want to pay attention
to is the "Native Resolution." This refers
to the true resolution (i.e. non-compressed, non-expanded)
of the projector. Ultimately, you want a projector that
matches the resolution of your computer exactly; if
an exact match is not available, then choose the level
that is slightly higher than the resolution of your
system. (If you plan on using the projector with many
different computers, then you want a projector with
a native resolution that is as high as the highest resolution
of all the units). Most projectors today support resolutions
that are higher than their native resolution by compressing
the number of pixels. However, much of the quality and
detail of the projected image is lost when this happens.
Do not be misguided by the maximum resolution capability
of the projector; instead, just focus on what the native
(true) resolution is. Resolution of projectors is differentiated
in four categories.
- VGA (640x480)
- SVGA (800x600)
- XGA (1024x768)
- SXGA (1280x1024)
- UXGA (1600x1200)
SVGA, or "800 x 600" - This
is a popular resolution today, because most notebook
computers are SVGA. Matching the projector resolution
with the computer resolution will produce the best results.
XGA, or "1,024 x 768" - XGA
projectors are generally more expensive, and are the
second most popular resolution format. Many of the newest
products are coming out in XGA. They are getting more
popular as prices drop and the use of XGA notebook computers
increases.
SXGA, or "1,280 x 1,024"
- SXGA products are high resolution, and notably more
expensive than XGA. These products are targeted for
high end personal computer users and low end workstation
users. They are used primarily for command and control,
engineering and CAD/CAM applications where acute resolution
of small details is important.
UXGA, or "1,600 x 1,200" -
UXGA is for very high resolution workstation applications
that are detail or information intensive. These are
expensive projectors that support a broad range of computer
equipment. Relatively few products on the market have
this native resolution. |
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ii. |
Brightness |
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Projectors come
in a wide range of light output. All other things being
equal, the brighter the projector, the more it costs.
When it comes to "optimum brightness" the
rule is simple: get the brightest projector you can
afford.
Brightness is measured in ANSI (American National Standards
Institute) lumens: the brighter the projector, the higher
the ANSI lumen rating.
In today's market, projectors can be grouped by ANSI
lumen output as follows:
Less than 1000 lumens - these are the
lowest light-output projectors available today, and
they are typically the least expensive. If you are on
a tight budget, there are a number of products in this
category that may be perfect for your needs. Keep in
mind that the low light output means that you will want
to make your presentations in a dark or dimly lit room
so that the image on the screen is not washed out by
ambient room light.
1000 to 2000 lumens - this lumen range
is a step up in performance and price. There are many
SVGA and XGA products in this class to choose from.
These machines are suitable for normal business conference
room and classroom use. Presentations should be done
with the room lighting reduced somewhat for best screen
viewing, although a totally dark or dimly lit room is
usually not necessary.
2000 to 3000 lumens - this represents
the high-performance range of the portable and semi-portable
projectors. Products in this class are suitable for
large conference rooms and classrooms. They offer more
flexibility in terms of ambient room light, since the
image is bright enough that a reasonable amount of room
light can be tolerated without washing out the image.
They also offer more flexibility in terms of audience
size since they can illuminate a larger screen without
much loss of image quality.
3000 lumens and up - the ultra-bright
projectors are in several performance classes unto themselves,
ranging from 3000 up to 12000 lumens or more. Prices
of these products also cover a wide range depending
on other performance characteristics. They are used
in a variety of large venue applications, including
board rooms, conference rooms, training rooms, auditoriums,
churches, concerts, nightclubs, and so forth. |
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Aspect ratio |
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The most popular aspect ratio
is 4:3 (4 by 3). Early television and computer video formats
are in a 4:3 aspect ratio, which means that the width
of the image is 4/3 times the height. Examples: A 15 inch
monitor is 12 inches wide by 9 inches high (9 x 4/3 =
12). A resolution of 640x480 is a 4:3 format (480 x 4/3
= 640). Other formats are 5:4 used by the 1280x1024 SXGA
resolution, 16:9 is used by HDTV, and 3:2 for 35mm slides.
It is important to think about weight of projector as
it might effect you if you are carrying your projector
too much, so it is good to have a projector with a weight
in a range of 2 to 3kg. |
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iv. |
Other Key Factors |
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Once you have your short list of projectors,
you can narrow it further by checking the manufacturer's
specifications and thinking about the following items:
Zoom lens: If you are using your
projector for mobile applications, a zoom lens can be
very handy. It gives you the ability to set the projector
at a convenient location, and adjust the projected image
size. Without a zoom lens, the only way to adjust the
picture size is move the projector forward or back. A
note of caution though--many of the micro-portables have
zoom lenses with limited range. A unit with a zoom factor
of 1.2x will only let you adjust picture size by 20%.
You can often move the projector a foot or two either
way and accomplish the same adjustment. Nevertheless,
if you have a fixed screen size you are trying to fill,
even a limited range zoom will make it easier to fine
tune the image size to the screen.
Keystone
Correction: In addition to the zoom lens feature,
mobile users should consider the benefits of keystone
correction. The keystone effect happens when you project
an image from any angle except straight onto the projection
surface and results in an image that is not completely
square. Many projectors now include a feature that corrects
horizontal keystone (when you are projecting downward
or upward). Others go a step further and provide additional
correction for vertical displacement (when you are projecting
from either side of the screen).
Contrast:
Contrast is the ratio between the brightest and
darkest areas of the image. Contrast ratios should be
high (400:1 or higher) to get the best video image or
the most legible computer/graphics image. Room light substantially
impacts contrast ratios. If you intend to use your projector
with the lights on, consider projectors with very high
contrast ratios.
Rear Projection Capability:
If you want to set up your projector to shoot from behind
a screen, it needs to have the ability to reverse the
image so that it looks right on the screen. Most projectors
have this feature today, but if you need it, you can eliminate
any projector that doesn't have this capability from your
short list.
Video Format Compatibility:
The standard video formats are NTSC, PAL, and SECAM. Many
projectors accept all three, but if you'll be playing
video from Europe, pay special attention to whether the
projector you're considering can accept PAL and SECAM
formats.
Video Signal Standards:
Most video devices accept composite and S-video as two
types of signal transmission. Almost all projectors will
accept both inputs. However, there is a new standard known
as component video. Some of the new DVD players offer
a component video output signal in addition to composite
and S-video. You will also be able to get component video
signals from some satellite systems. Televisions and projectors
that are equipped to handle the component video signal
will produce a superior video image than those which cannot.
If you are interested in optimizing video performance
and you have a video source that offers component video
output, check to see which of the projectors on your list
are capable of accepting a component video signal. The
spec sheet may say component video, or alternatively (Y,
R-Y, B-Y) or YPbPr.
Ceiling Mountable:
If you want to mount your projector on the ceiling, it
will need the capability to project the image upside down.
The large majority of projectors will do this today, but
verify that this feature exists. Also, you must verify
that a ceiling mount exists as an option for this product.
Universal Power Supply: Universal power supply means the
projector will automatically detect different voltage
levels, such as 110 volts in the United States or 220
volts in Europe, and adapt easily to them both. If you
plan to travel with your projector in countries with different
power systems, this is a must.
Multiple
Computer Ports: If you want to connect multiple
computers or video sources to the projector simultaneously,
you will need multiple input jacks to accommodate this.
For example, you may want to connect a notebook computer
and a desktop computer to support two consecutive presentations,
or two different presenters. If your projector only has
one computer source, you'll have to unplug the notebook
and plug in the desktop between speakers. Check to make
sure the projector has enough connections to support your
typical use.
Data Signal Ports:
Most importantly, make sure the projector you choose supports
the computers you intend to use now and in the near future.
This is a significant investment and the pace of change
in the computer industry should be a consideration. PC
and PC compatiables are nearly always supported with a
direct connection, but Macintosh may be a separate connector
or require an adaptor. If you are using a workstation,
check that the models you intend to use are supported
in the manner you intend to use them and if adaptors are
needed, know whether they are included or an additional
cost item. |
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