We will stick to text and graphics as we take you through this section. The reason for this is simple: moving images do not need the level of detail and accuracy that a picture in a PowerPoint file or numbers within an Excel sheet require.
Technology: Liquid Crystal Display (LCD) and Digital Light Processing (DLP) are two technologies used in a projector. A DLP projector uses an optical semiconductor which contains a rectangular array of up to 1.3 million hingemounted microscopic mirrors. These tilt either toward a light source (ON) or away from it (OFF) creating a light or dark pixel on the projection surface.
An LCD projector consists of LCD panles and "Dichroic" mirrors which first split light into the consituent R, G and B colours. The panels are used to block differing amounts of each colour, allowing a total of 16.7 million colours to be produced when the light paths are recom
bined in a dichroic cube. The recom¬
bined light is then launched via the
projection lens onto the screen.
in terms of quality, there is little to differentiate between an LCD and a DLP projector. Most people are likely to opt for a DLP solution because it is normally the smaller of the two and the image quality, especially where movies are involved, is slightly better.
Resolution: Resolution determines the sharpness and clarity of an image. The most common resolution is SVGA or 800 x 600 pixels. This is sufficient for most users, and SVGA projectors are the cheapest available in the market.
Define your task here if you are looking at meetings with nothing but presentation slides, SVGA is good enough. But if you are part of a sales team and find yourself pitching spreadsheets full of projected growth and earnings to your immediate superiors, you might want to look for an XGA or a 1,024 x 768 pixel projector. The larger number of pixels that an XGA solu
tion affords will bring greater clarity to the small text so prevalent in a spreadsheet. You can take this forward: the finer the detailing on your presentation (maybe a CAD drawing?) the higher the resolution required, and the greater the price you will pay. You thus have SXGA (1,280 x 1,024) and UXGA (1,600 x 1,200) solutions, the latter being a rare breed due to their high asking price.
One final point to consider a projector has a "native" resolution; the native resolution for an SVGA projector will be 800 x 600, for an SXGA unit 1,280 x 1024 and so on. Try and match the native resolution of your projector to the screen resolution of either your laptop or the PC from which you are sourcing the presentation. If the projector's native resolution is different from your computer's screen resolution, the output will appear fuzzy due to "scaling."
Brightness: This directly affects the size of the audience your projector can address. The brighter the projector the better, and you should always go for the brightest unit you can afford. Define the nature of your presentation first. If your business showcases more videos, or if you are using the projector at home, brightness loses importance since these tasks are usually done in
The image captured by a video camera is in the RGB format. Passing the three colour signals separately will improve the image quality, but doing it without compression is a bad idea as it consumes lots of bandwidth. Component video solves this problem by compressing an RG13 signal and delivering it to the projector.
The component signals communicate the luminance in an image and the colour information. Luminance is denoted by Y, whereas the other two signals, which are red and blue, are denoted by R Y and B y. Since a projector already has luminance and red and blue colour information, it simply needs to fill
a dark room and visibility is therefore not a problem. If, however, you are presenting to a group of note takers or are teaching a workgroup, your room will need some sort of illumination, and so your projector's brightness (
to the fore. You can alleviate the need for bright units (since the associated cost increases with brightness) by employing reflecting screens for your projecting. Note that a typical wall is generally the worst place to project upon.
Finally, the size of your audience will also play a part. The larger your audience, the larger and brighter the projected image will need to be.
Brightness is measured in ANSI lumen or just lumen. An entry level projector carries 1,000 lumen or less; as this rating increases, so does the price. A 3,000 lumen projector will classify as a high end unit, but a 12,000 lumen unit is not unheard of and is often employed in public places like nightclubs.
Weight: The portability of a projector becomes a point of concern if you are the travelling type. Anything more than 2 kg should generally be shunned. Some projectors come along with a card readers that can handle CompactFlash (CF) or SecureDigital. (SD) cards these let you carry your presentation on handy flash cards and you no longer need to lug your laptop along for the meeting! Another boon for the traveller is a wireless projector an ideal mate for an Intel Centrino based laptop or a similar Wi Fi match.
The factors listed above serve as a level one filter when making a buying decision for a projector. Once you have decided on the right combination of the features and settled on a price, you will still have other choices to make (more, if you look to the grey market). To further refine your needs, consider these "bonus features", if you will:
Keystone Correction: An image that is not completely square is a result of the keystone effect. This happens if your projector is not perpendicular to the screen upon which it projects, making for a trapezoidal image. Look for a projector that includes either a horizontal keystone correction feature (when projecting downward or upward) or a vertical one (when projecting sideways to a screen).
Contrast: The ratio between the lightest and the darkest areas of an image, the contrast should be at least 400:1. If you are projecting in a dark or dimly lit room, the contrast ratio will not be as
high as when you are projecting in a
well lit room.
Video Signals: Most projectors can
handle both composite and S Video transmissions. Some projectors can also handle "component" video, and these should be considered if your source or presentation supports it as they give images of a higher quality. See box "Demystiffing Component Video" below for more.
Computer Ports: If you need to connect multiple sources to your projector, the unit must have the required number of ports. For example, if you plan to present alternating from your laptop and PC, the projector needs to have at least two video ports.
Rear Projection: If you want your projector to display from behind a screen, it should be capable of inverting the image before projecting. Look for rear projecting units for this feature.
Zoom Lens: A zoom lens alleviates the need to shift your projector to increase or decrease the size of a projected image. A projector with a 1.2X zoom lens will increase image size by about 20 per cent. This zooming is vital to fill a fixed screen size from a given distance.
To Sum It All Up: Resolution and brightness are vital; the more the better and the more expensive your purchase will be. Contrast ratio is also important, especially if your presentations happen in bright rooms.
