LCD vs DLP Projector Technology
LCD  delivers a somewhat sharper image than DLP at any given resolution. The difference here is more relevant for detailed financial spreadsheet presentations than it is for video. This is not to say that DLP is fuzzy--it isn't. When you look at a spreadsheet projected by a DLP projector it looks clear enough. It's just that when a DLP unit is placed side-by-side with an LCD of the same resolution, the LCD typically looks sharper in comparison.

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. 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.  Contrast ratio is a difference in that LCD doesn't produce absolute black, whereas a DLP projector can aceive ratios of up to 2000:1 and more this is significant for home movies in a darkened room where the blackness can be seen but since business data applications usually take place in a well lit room it is of no consequence that the LCD does not have the deep black ratio..  

DLP is the newer technology and it has been developed to improve the picture over LCD and that DLP projectors tend to be smaller and lighter, have better contrast, and don't suffer the same pixelation problems as LCD projectors.  One benefit of LCD is that it has historically delivered better color saturation than you get from a DLP projector. That's primarily because in most single-chip DLP projectors, a clear (white) panel is included in the color wheel along with red, green, and blue in order to boost brightest, or total lumen output. Though the image is brighter than it would otherwise be, this tends to reduce color saturation, making the DLP picture appear not quite as rich and vibrant.  Overall however, most LCD projectors have the best deep colour brightness and performance advantage in this area.

A third benefit of LCD is that it is more light-efficient. LCD projectors usually produce significantly higher ANSI lumen outputs than do DLPs with the same wattage lamp. In the past year, DLP machines have gotten brighter and smaller--and there are now DLP projectors rated at 2500 ANSI lumens, which is a comparatively recent development. Still, LCD competes extremely well when high light output is required. 

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Contrast

High Contrast	Low Contrast

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 2100 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- 2000 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 2200 to 3600 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 3500 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. Boardroom projectors in particular should be quiet as you don't want to be sitting in suspense at a quiet point in the negotiations listening to the projector fan

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 50dB.

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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

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
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
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.
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.
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.
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)
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.
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.

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, designed for viewing movies and HDTV in wide screen format. The 16:10 format is found in data projectors since it matches the output format of widescreen laptops with typically 1280 x 800 pixel resolution. Matching the laptop output pixel count to the projector native resolution results in the clearest picture reproduction - important for data presentation. 

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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.

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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