Selecting a Projector Suitable to Your Needs
By: James C. Long and Jennifer Skates

A video projector can be used in many different venues. They are most widely used in conference room presentation, classroom training, sanctuary or auditorium presentation, and home theater applications. The cost of projectors can vary significantly from model to model. With features ranging from simple to advanced, how do you find out which one will best suit your needs and your budget? You also don't want to worry about service issues or having to replace a lamp that may soon be obsolete. That's why it's important to buy from an experienced dealer who knows about the model, the manufacturer, its features and capabilities.

Resolution
A video projector takes a video signal and projects the images on a projection screen. The higher the resolution, the more detailed your image will be. All video projectors use a bright light to project an image, but one of the more important features to consider is the resolution quality. The most common display resolutions available are SVGA (800 x 600), XGA (1,024 x 768), SXGA (1,280 x 1,024) and 720p (1,280 x 720).

The resolution you need depends on the type of images you'll be projecting. For large fonts and graphics, an SVGA projector will work fine. However, if you're projecting video, background images with text, or detailed charts, a projector with XGA resolution or higher will make sure your message comes across legibly.

The cost of the projector is not solely determined by its resolution. Other determining factors in cost are light output, contrast and acoustic noise output.

Brightness
The brightness of a projector is measured in lumens. This lumen rating tells you several things about the projector. One with a lower lumen rating will work best in a room that is typically dark (i.e., no bright windows or ambient light to cause your image to look "washed out" and hard to see). Therefore, a projector with higher light output is required for a larger screen or a room with high ambient light. A rating of 1,000 to 1,500 ANSI lumens or lower is suitable for smaller screens with controlled lighting or low ambient light. A lumen rating of 1,500 to 3,000 is suitable for medium-sized screens with some ambient light. Over 3,000 lumen rating is appropriate for very large screens in a large room with no lighting control such as a large church sanctuary or auditorium.

The biggest advantage to having a projector with a very higher lumen rating is the ability to project bright enough for you to leave the majority of the lights on without sacrificing your image clarity or color. As far as performance and legibility are concerned, a projector that's bright enough to leave most of your lights on (especially in classrooms) can also help you make sure everyone is paying attention.

Contrast
The contrast ratio is the ratio between black and white. This complements the brightness of your projector. A high contrast ratio means whiter whites and blacker blacks. This ratio is usually listed anywhere from 300:1 (300 to 1) up to 3,000:1 (3000 to 1) and anywhere in between. The contrast ratio tells you how many more times darker the color black will appear than the white, which makes video and still images much clearer and easier to see. A low contrast ratio means that a true black may appear gray instead, especially in brighter rooms. The difference in performance between a low and high contrast ratio also depends a lot on the human eye, the amount of ambient light, and the type of material that will be projected. However, for image readability and clarity, the higher the better.

Projected image size is important because the total amount of light does not change, as size increases, brightness decreases. Image sizes are measured in linear terms diagonally. Larger images require more light (proportional to the image area, not just the length of the side). Increasing the diagonal measure by 25 percent reduces the image brightness by 35 percent.

Video Projector Technologies
To date, there are five prominent video projector technologies. They are LCD, DLP, LCOS, D-ILA and CRT. The current dominant technology for expensive portable digital projectors is Texas Instruments' DLP technology, with LCD projectors dominating the less-expensive market segment.

1. LCD
An LCD (Liquid Crystal Display) projector produces digital images for viewing through three separate LCD glass panels, one each for red, green and blue. This is the simplest system, making it the most commonly affordable. Though LCD projectors are less expensive, they can sometimes be bulky. One of the most common problems is with pixelation effect. While they generally perform best where color reproduction is critical, the LCD projector will focus so precisely on each pixel that this can cause disadvantages with viewing video.

2. DLP
DLP stands for Digital Light Processing and is based on an optical semiconductor. This technology was developed by Texas Instruments. A DLP projector reproduces images using a single chip made up of millions of microscopic mirrors, with a color wheel of red, green and blue. These mirrors, called digital micromirror devices, reproduce an image with maximum fidelity. A typical DLP projector can create more than 16 million colors. Although DLP projectors are more expensive, they are extremely lightweight and portable, and they are most preferred for their cinema-like quality and lamp efficiency.

3. CRT
A CRT projector uses cathode ray tubes. This usually involves a red, green and a blue tube. It can produce the blackest blacks as well as the full range of color, making it one of the better choices for projecting film-like images. The CRT projector also has a long projection life when compared to other projectors. Plus, minimal maintenance is required (unlike projectors that use lamps). These are most often used in very expensive fixed systems in the home or installed systems in a church or school.

4. D-ILA
D-ILA stands for Digital Direct Drive Image Light Amplifier. Developed by JVC, this technology is a more reflective type of LCD. It is based on a microchip design using next-generation D-ILA chips designed to produce higher resolutions, better contrast ratios, less image artifacts, and better tone and color. A single microchip has 2,048 x 1,536 pixels, making it possible to display HD images at full resolution (up to 1,080p depending on the projector).

5. LCOS
LCOS stands for Liquid Crystal on Silicon. It is a combination of LCD and DLP technology, which uses liquid crystals instead of mirrors. There are typically three chips, one each for red, blue and green light modulation. The lack of a color wheel eliminates any problem of rainbow artifacts, eye-strain or headaches, which some people are susceptible to when viewing images with a single-chip DLP projector. Generally, a LCOS projector has very high resolution (SXGA, 1,365 x 1,024) and is usually more expensive as a result. One of the biggest advantages is the pixel resolution, resulting in seamless video images with a smooth, more natural look.

Projection Screen Size
What size screen do you need? This all depends on the size of your room and your projector's type of lens (throw ratio) as well as its throw distance and image size capability. However, the screen and projector must work together. It's important to make sure your projector won't require more distance to the screen than your room will allow. The image size specifications on your projector will give you an idea of how large or how small an image the projector is capable of producing. This is measured diagonally. The throw distance determines the size of the projected image by stating how far away the projector should be in order for the lens to create a specified image size. Another important characteristic to note is your projector's lens type. Each lens will list its throw ratio and throw distance in the manufacturer's specifications. This ratio (unless you have a zoom lens) is fixed.

Once you've determined the available space you have, and the image size you're looking for, this easy formula can help you determine the throw distance. Let's say, for example, your projector's lens has a set throw ratio of 2, and your church is looking to project a 6-foot image. So, 2 (lens throw ratio) = (D) Distance needed divided by (W) 6-foot image. To create a 6-foot image, you would need to place the front of your projector lens 12 feet away from the screen, since 2 equals 12 divided by 6.

In conclusion, your venue size, the amount of ambient light and budgeting concerns are the three most important factors in determining what kind of projector to buy. These are simply some guidelines to help in picking a projector that is suitable for your needs.

James C. Long is in marketing and Jennifer Skates is a copywriter with Long's Electronics, www.longsav.com.