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Shedding Light on Projector Technology Believe it or not, people were using projectors, or at least dreaming about
them, centuries before the advent of silent movies. In fact, a fellow named
Johannes de Fontana rendered the first drawing of a projector-like machine back
in 1420. And in 1645, a Jesuit scholar illustrated a device for reflecting
sunlight from a mirror, through a lens and on screen. He called his invention a
magic lantern! Today's technology is quite a bit more complex, but the idea
remains the same - to project an image on a smooth surface so that many people
can see and enjoy it. Here is a brief synopsis of the nuts and bolts of
present-day projector technology.
The Three Types of Projectors There are three major types of projectors: Standard LCD (Liquid Crystal
Display), Polysilicon LCD, and DLP (Digital Light Processing) projectors.
Standard LCD
Standard LCD projectors have one panel of LCD glass that controls the three
primary colors. Standard LCD projectors are becoming less common as polysilicon
LCD and DLP projectors gain popularity. They usually display a much brighter
image than DLP. However, their transmission design limits the amount of time
they can be used. LCD-based projectors often operate effectively only a short
time, with image deterioration present after 8-10 hours. Because LCD projectors
transmit light through LCD chips, then through the optics and onto the screen,
heat is transferred to the LCD chips from the light source. This causes the LCD
chip to deteriorate and will probably result in severe image loss and can
permanently damage the LCD projector.
Polysilicon LCD
These projectors control colors through three panels and are higher in quality
than standard LCD projectors. Projecting through 3 panels allows polysilicon LCD
projectors to have higher color saturation than a standard LCD projector.
DLP (Digital Light Processing)
The most common type of projector on the market, DLPs use a single chip with
thousands of micro mirrors to modulate the lamp's light and project it through
the lens. DLP systems are composed of over 400,000 tiny mirrors, which modulate
light from a lamp and project the "modulated" signal out through the lens onto a
screen. This technology is also referred to as DMD (Digital Mirror Device). This
mirror configuration prevents heat from having an adverse effect on the
projector's components. Thus, DLP projectors can operate continuously with no
discernable loss in performance. The only loss comes from slow bulb decay, which
gradually reduces brightness. Simply replacing the bulb will generally return to
the DLP projector to its original quality.
How to Choose the Ideal Projector for Your Needs It's All About
Resolution, Brightness and Weight & Size
Although projector technology is complex, deciding what kind of machine you need
should be a relatively simple process involving three major considerations:
resolution brightness, and weight (and size). Other factors such as contrast
ratio, color reproduction, inputs for composite and S-video, DVD, and extra
innovations, will also play a role in your decision. Please see our glossary
below for more information on these extra features.
Projector Resolution
The sharpness and clarity of the picture on screen is determined by a
projector's resolution, which is the sharpness of the image projected based on
the number of pixels. The higher number of pixels, the better. However, the
higher the resolution, the more expensive the projector. High-resolution
projectors can show more picture details than low-resolution projectors.
Low-resolutions projectors are much less expensive and can produce images that
arte just as bright and attractive as higher resolution machines. Unless you
must display fine details, lower-projection units are your most cost-effective
value.
Categories of Resolution
Projectors come in four categories of resolution: UXGA (1600 x 1200)
- For very high-resolution workstation applications that are detail or
information intensive. Very expensive. SXGA (1280 x 1024) -
High-resolution; more expensive than XGA. Used for high-end personal computer
users and low-end workstation users. XGA (1024 x 768) - Ideal for
relatively high-resolution images from videos, spreadsheets and graphics. More
expensive than SVGA. XGA has become the most popular resolution for business
applications. SVGA (800 x 600) - Very popular because of low price and
great images. Excellent for projecting simple graphics and presentations. SVGA
is excellent for watching movies, DVDs or TV, but not optimal for computer
graphics or PowerPoint slides.
Most units have a standard of 640x480 pixels or 800x600 pixels (VGA and SVGA,
respectively). Higher resolution models are useful if you need to project more
of a screen, such as a full layout of a document or drawing. Examples of higher
resolutions are XGA (1024x768) and SXGA (1280x1024).
Before you start shopping, keep in mind what your needs are. If you're going
to be using your projector for general business presentations such as Power
Point, SVGA is your best choice. If you present materials that have lots of
numbers you will be better served with higher resolution such as XGA. If your
information is highly detailed, technical data such as engineering drawings you
will probably need a very high resolution SXGA projector. It is best to match
the resolution of your projector with the resolution of the computer you intend
to use with it. Although most projectors can project input signals other than
their native resolutions, you will lose some sharpness and detail if the
resolution isn't the same as your computer.
Brightness - ANSI Lumens Your presentation isn't going anywhere if
your projector can't produce enough light to throw images across a room and onto
a screen. Accordingly, the brightness (measured in ANSI lumens) of your
projector is worth investigating. Generally, the brighter the room, the brighter
projector lamp you will need. When deciding how much brightness your projector
has to have, keep in mind how dark the rooms will typically be for your
presentations and how far your projector will be from the screen. The more light
in the room or the farther away the projector, the brighter your projector
should be. ANSI lumens for projectors currently range from 400 to 1,000 for
ultralights up to as much as 10,000 for fixed machines. For on-the-road
presentations, 500 to 1,000 ANSI lumens should be fine. Larger conference rooms
will need 1,000 to 2,000 lumens, while fixed installation machines will need to
project between 2,500 and 10,000 lumens to handle auditoriums or other large
venues. The brightness of a projector can sometimes be misrepresented, so be
sure to check the brightness of the individual projector and not the published
brightness of the model line. The brighter the room or the farther away your
setup, the brighter the lamp you'll need. Generally, the larger size image you
want to project, the higher brightness you will need to project the image. As a
rule of thumb, when the size of the image is doubled, the brightness will need
to be quadrupled. The LCD systems with less than 400-400 ANSI lumens can project
black and white Excel images in dark room settings, they may not have enough
illumination to keep multicolored presentations from appearing washed out.
Lumen Categories
3000 lumens and up - Ideal for a variety of large venues such as board
rooms, conference rooms, auditoriums, concerts, nightclubs, etc.
2000 to 3000 lumens - This is the high-performance range for portable
and semi-portable projectors. Ideal for large conference rooms and classrooms.
Projectors with 2000 to 3000 lumens brightness 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 losing much image quality.
1000 to 2000 lumens - These projectors are suitable for normal
business conference room and classroom use and work best when the room lighting
is reduced, but not necessarily totally dark. Most standard-use projectors fall
into the 1000 to 2000 lumen range. Projectors with 1000 ANSI lumens or greater
have sufficient brightness for home theater use.
1000 lumens or less - Satisfactory if you have a limited budget.
Projectors with 1000 lumens or less brightness have the lowest light output and
are usually the least expensive. Because of the low light output, they work best
in dark or dimly let rooms where ambient room light will not wash out the image
on the screen.
Choosing Size and Weight Projectors come in three general size
categories - ultralights or personal projectors, conference room projectors and
fixed installation projectors. If you buy an ultralight you can take it
anywhere. Conference room projectors are heavier and ideally remain at the work
place or home. Fixed installation projectors are extremely heavy - up to 100
pounds - and remain in one place, such as an auditorium.
Ultralights (Personal) These are ideal for the executive who makes
frequent presentations on the road. These bantamweight projectors seem to get
lighter and lighter every year. Some of the latest models weigh less than five
pounds. Designed to provide portable solutions for the business community,
Ultralight projectors sacrifice brightness and some extra features.
Conference Room - These are high-performance projectors that are
heavier, brighter and more adaptable to larger rooms than the Ultralights.
Conference Room projectors frequently include many extra features lacking in
smaller machines.
Fixed Installation - The heavyweight among projectors - both in size
and performance - the fixed or in-house projector occupy permanent residence in
auditoriums or presentation halls. They are the most expensive projectors.
Other Considerations that Can Influence Your Buying Decision
Contrast - Ratio between darkest and brightest areas of the image.
High contrast ratios deliver whiter whites and blacker blacks. Your projector
could have a great lumens rating, but if the contrast ratio is low, your image
will look washed out. Contrast ratios of 1000:1 are good, but 2:000:1 or higher
is excellent.
Rear Projection Capability - If you want to set up a rear-projection
system, the model must have the ability to reverse the image so that it appears
correctly on the screen. Most models have this feature.
Video Format Compatibility -Standard formats are NTSC, PAL and SECAM.
Many projectors accept all three.
Video Signal Standards - Most video devices accept composite and
S-Video. Almost all projects will accept both inputs. Some new DVD players and
some satellite systems offer a new standard known as component video. TVs and
projectors equipped to handle component video signal will produce a superior
video image.
Ceiling Mountable - If you want to mount your projector on the ceiling
it will need to have the ability to project the image upside down. Most
projectors can do this.
Lens and Optics Zoom lenses are standard with most projectors. Some
zoom lenses operate manual; others are motorized, which allows you to adjust the
image remotely. Projector lenses are made of glass or plastic. Glass lenses give
you a clearer image, but weigh more than plastic. If you are going to travel a
lot, weight is a consideration.
Lamp Life - Lamp life is generally between 1,000 to 2,000 hours. A
lamp life of 2,000 is excellent.
Projector Glossary
- ANSI Lumens - Industry standard measurement of a projector's brightness.
Depending on lamp, optics and projector design, ANSI lumens on projectors range
from 200 to 10,000.
- Color Dynamics: "The whitest whites, reddest reds, etc." High color dynamics
are a result of dynamic range/contrast ratio's. When we describe a unit as
having excellent color dynamics, the practical description might be "rich
colors, excellent definition, high contrast".
- Component Video: Component Video is a method of delivering quality video
(RGB) in a format that contains all the components of the original image. These
components are referred to as luma and chroma and are defined as Y'Pb'Pr' for
analog component and Y'Cb'Cr' for digital component. Component video is
available on some DVD players and projectors.
- Contrast Ratio - The contrast between the brightest white and the darkest
black. Higher contrast ratios offer brighter colors and better details.
Preferably, you'll want to choose a contrast ratio of at least 1:000 to 1.
- DLP - Digital Light Processing. A relatively new and popular projection
technology developed by Texas Instruments. DLP projectors tend to offer brighter
and m ore continuous images than their LCD-based counterparts.
- Document Camera - An added feature on some projectors, document cameras can
project objects or other images not easily entered into a computer. They work on
the same principle as overhead projectors with the functionality of LCDs.
- F-number - Refers to the amount of brightness that a lens allows through to
the screen. Ideally, the f-number should not deviate much from different zoom
angles.
- Image Size - The size of a projected image, usually measured diagonally.
Make sure to test out the maximum image size for yourself, since manufacturer
spec sheets can be rather subjective.
- Keystone -Keystoning occurs when the projector is not perpendicular to the
screen, thereby creating an image that is not rectangular.
- Keystone Correction -Keystone correction makes a projected image
rectangular. This can be accomplished by positioning the projector to be
perpendicular to the screen. Since this is not always possible, most projectors
are equipped with keystone correction that allows the image to be keystone
corrected (made rectangular) by adjusting optics, making mechanical adjustments,
or applying digital correction to the image. Keystone correction can be one or
two dimensional and manual or automatic depending on the projector and the
manufacturer.
- Polysilicon LCD - Projection technology, which utilizes a three-layer LCD,
panel design. Three separate primary color panels that are used to produce the
desired color.
- Resolution - The number of screen pixels that can be displayed by the
projector. Most units have a standard of 640 x 480 pixels or 800 x 600 pixels
(VGA and SVGA, respectively). Higher resolution models are useful if you need to
project more of a screen, such as a full layout of a document or drawing.
Examples of higher resolutions are XGA (1024 x 768) and SXGA (1280 x 1024).
- Native Resolution - The computer resolution that optimizes the projector
resolution. When buying a projector you should always match the resolution of
your notebook to the native resolution of a projector. Native Resolution refers
to the number of physical pixels in a display device. For example, an SVGA
projector has 800 physical pixels of resolution horizontally and 600 pixels
vertically or 480,000 total pixels. This is the native resolution of the
projector. Projectors are capable of projecting greater or smaller resolution
images into the same physical resolution through scaling. Scaling reduces the
resolution of larger images and increases the resolution of smaller images to
match the native resolution of the display device. This type of digital scaling
always produces some artifacts in the image that are more apparent when viewing
text than graphics or video.
- TFT (Thin Film Transistor) LCD - Projection technology, which uses only one
transparent panel of LCD, cells.
- Throw Distance - Also known as projection distance. The distance from
projector to screen.
- Video Standards - The type of video inputs an LCD projector can accept.
Leading standards include NTSC, SECAM and PAL, with NTSC being the North
American video standard.
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