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 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.
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.
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.
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.
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.
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.