General discussion


Which is the best Data Projector to buy?

By barry.hendriks ·
(Some research I have done on the internet to find the answer to this question)

It all depends on the size of your wallet and what you intend to do with your projector.

What I do recommend is the following criteria should be looked at to make an informed decision: (Compare apples to apples and pears to pears)

1. Screen resolution: 1024 x 768 or better. (XGA)
? VGA = 640 x 480 pixels (obsolete)
? SVGA = 800 x 600 pixels
? XGA = 1024 x 768 pixels
These terms represent the various fixed resolutions of a projector's internal panel, onto which an incoming signal must first be mapped before it can then be projected. SVGA and XGA are currently the most common resolutions in the marketplace. SVGA, being of lower resolution (800 pixels wide x 600 pixels high), is less expensive than XGA (1024 x 768), but doesn't provide sufficient resolution to do justice to HDTV signals.

Presentations of PowerPoint slides, Excel spreadsheets: For normal PowerPoint slides a resolution of 640 x 480 would be suffice but the moment you looking at spreadsheets etc the need arises to be able to use 800 x 600 or even better 1024 x 768. So in order to cater for future needs, a resolution of 1024 x 768 or better is recommended.

Do you want to use it to replace your current TV set-up at home? The normal TV screen display is 640 x 480. It that is all you want to do and never upgrade to HDTV or use a DVD player ? This is all you need.
BUT again, to cater for future needs 1024 x 768 is recommended.

If you plan to watch a lot of television on your projector, you need to be aware of two issues.

One. You must have a tuner to receive HDTV signals. Your projector does not come with a built-in tuner like a regular TV set does. You can either use a video recording machine or the output of a computer TV tuner card. Just make sure the tuner can output an HDTV quality signal, and that the projector has the proper input.

Two. If you want to watch TV using your projector, be sure to have an additional lamp. Projector lamps can last anywhere from 1000-2000 hours, and are not cheap to replace. Typically a replacement lamp will sell for about R5000+. You may want to consider a projector with a longer lamp life when you purchase. You may also want to consider a plasma screen, which has a much longer life expectancy (about 32,000 hours).

2. Aspect ratio: 16:9 and 4

Normal TV use 4:3, HDTV and DVD movies are optimised for 16:9

3. High colour matching: 16.7 Million colours

Trying to watch anything on screen in 256 colours is a BAD experience!

4. Horizontal Frequency: 70 KHz +

This is the speed at which one single line is drawn across the screen, the faster the better. 70KHz or better is recommended.

5. Vertical Scan rate: 75 Hz +

This is the speed a complete screen is redrawn from top to bottom. The electricity supply in South Africa is 220V @ 50 Hz. Anything close to 50 Hz or below results in screen flicker. The higher the frequency the better. 100 Hz is recommended.

6. LCD or DLP technology?: LCD

- DLP colour change over time.
- DLP use a mechanical device ? More wear and tear
+ DLP have better contrast and the lack of pixilation
+90% fill factor. Because the gaps between pixels are minimized

+LCD delivers a sharper image
+LCD is that it is more light efficient (Higher lumens with same wattage lamp)
-LCD has pixilation
-80% fill factor. Because of the size of the gaps between pixels.

7. Contrast ratio: 800:1

In reality, though the difference between projectors rated at 400:1 vs. 800:1 is quite noticeable, the difference is not so dramatic between products rated at 900:1 vs. 1800:1. Once you get to contrast ranges of 900:1 or higher, blacks appear as solid black and shadow details resolve quite nicely.

8. Lumen (Brightnes of the picture projected): Depends

To achieve the same brightness in a well lit room and a dark no lights room may require two completely different projectors! Some technical people say 1000 lumens is enough for a well lit room, others say 2000 is enough. I would like to suggest at least 1800 lumens to cater for both worlds.

9. Lamp Life Expectancy: 2000 hours or better

2000 hours means 40 hours per week x 50 weeks (Approx 1 year)

LCD vs. DLP: Which is the best?

You don't have to shop around the projector market very long before discovering that "LCD" and "DLP" somehow refers to two different kinds of projectors. You might not even know what LCD and DLP are before asking the obvious question "which one is better?"
The answer is simple. Sort of. LCD and DLP each have unique advantages over the other, and neither one is perfect. So it is important to understand what each one gives you. Then you can make a good decision about which will be better for you.
The Technical Differences between LCD and DLP
LCD (liquid crystal display) projectors usually contain three separate LCD glass panels, one each for red, green, and blue components of the image signal being fed into the projector. As light passes through the LCD panels, individual pixels ("picture elements") can be opened to allow light to pass or closed to block the light, as if each little pixel were fitted with a Venetian blind. This activity modulates the light and produces the image that is projected onto the screen.
DLP ("Digital Light Processing") is a proprietary technology developed by Texas Instruments. It works quite differently than LCD. Instead of having glass panels through which light is passed, the DLP chip is a reflective surface made up of thousands of tiny mirrors. Each mirror represents a single pixel.
In a DLP projector, light from the projector's lamp is directed onto the surface of the DLP chip. The mirrors wobble back and forth, directing light either into the lens path to turn the pixel on, or away from the lens path to turn it off.
In very expensive DLP projectors, there are three separate DLP chips, one each for red, green, and blue. However, in DLP projectors under $20,000, there is only one chip. In order to define colour, there is a colour wheel that consists of red, green, blue, and sometimes white filters. This wheel spins between the lamp and the DLP chip and alternates the colour of the light hitting the chip from red to green to blue. The mirrors turn on and off based upon how much of each colour is required for each pixel at any given moment in time. This activity modulates the light and produces the image that is projected onto the screen.
The Advantages of LCD Technology
One benefit of LCD is that it controls red, green, and blue independently through three separate LCD panels. That means you can adjust brightness and contrast of each colour channel individually. In LCD projectors with good controls on board, this can enable the projector to achieve very good, and sometimes excellent colour fidelity. In most single-chip DLP projectors, colour is fixed and defined to a large degree by the physical colour wheel and the colour temperature of the lamp, which changes over its usable life. So while DLP technology has gotten much better at reproducing accurate colour, good LCD projectors still have a slight performance edge in this area.
LCD also delivers a somewhat sharper image than DLP at any given resolution. The difference here is more relevant in data than in video. This is not to say that DLP is fuzzy--it isn't. When you look at a financial spreadsheet projected by a DLP projector it looks clear enough. It's just that when a DLP is placed side-by-side with an LCD, the LCD typically looks a little bit sharper in comparison. However, it isn't something you'd notice except in a side-by-side comparison.
A third benefit of LCD is that it is more light efficient. LCD projectors 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--there are now DLP projectors rated at 2000 ANSI lumens, which is a comparatively recent development. Still, LCD competes extremely well when high light output is required. All of the portable light cannons in the 15 lb weight class putting out 3000 ANSI lumens or more are LCD projectors.
The Advantages of DLP Technology
There are several unique benefits that are derived from DLP technology. One of the most obvious is package size. Since the DLP light engine consists of a single chip rather than three LCD panels, DLP projectors tend to be more compact. All of the current 3-pound miniprojectors on the market are DLPs. Most LCD projectors are six pounds and up.
Another DLP advantage is that it can produce smooth, high contrast video. DLP has been well received in the home theatre world primarily due to two video quality advantages?better contrast and the lack of pixilation. Earlier generations of LCD projectors were notorious for their inability to generate acceptable black levels and contrast, and to resolve subtle shadow details. Blacks on LCDs looked grey and shadows appeared muddy and indistinct. In comparison, DLP projectors did a much better job.
While both technologies have produced improvements in contrast in the past year, DLP projectors still tend to outperform LCDs in this regard. However the practical performance advantage in black levels and contrast that DLP holds over LCD has been reduced somewhat. Sony's newly released VPL-VW12HT carries a manufacturer's spec of 1000:1 contrast, and Sanyo's new PLV-70 is rated at 900:1. Meanwhile, the latest DLP products geared toward home theatre are rated has high as 1800:1. However, one should not place too much emphasis on the specs. In reality, though the difference between projectors rated at 400:1 vs. 800:1 is quite noticeable, the difference is not so dramatic between products rated at 900:1 vs. 1800:1. Once you get to contrast ranges of 900:1 or higher, blacks appear as solid black and shadow details resolve quite nicely. Increased contrast can yield relatively subtle improvements, but there are other factors, which contribute to image quality that become equally if not more important.
Reduced pixilation is another benefit of DLP. LCDs were always known for their visible pixel structure, often referred to as the screen door effect because it appears as though the picture is being viewed through a screen door. Historically, LCD technology has had a hard time being taken seriously among many home theatre enthusiasts (quite understandably) because of this flaw in the image.
DLP technology went a long way toward eliminating the screen door effect. In SVGA (800x600) resolution, DLP projectors have either a muted pixel structure or an invisible pixel structure depending upon the size of the projected image relative to the viewing distance (the larger the image the more visible the pixels). Conversely, SVGA-resolution LCD projectors uniformly have a clearly visible pixel grid at just about any screen image size. For this reason, we don't recommend SVGA-resolution LCD projectors for home theatre use except for those on the most limited of budgets.
Three developments have served to close the gap between DLP and LCD in the area of pixel visibility. First was the step up to XGA resolution (1,024x76. This higher resolution uses 64% more pixels to paint the image on the screen, as compared to an SVGA-resolution projector. The inter-pixel gaps are reduced in XGA resolution, so pixels are denser and less visible. In XGA resolution, DLP projectors have an invisible pixel grid on any typical home theatre screen no matter how big. LCD projectors with standard XGA panels still have a visible, but much reduced screen door effect.
Second, the inter-pixel gaps on all LCD machines, no matter what resolution, are reduced compared to what they use to be. So even the inexpensive SVGA-resolution LCD projectors have less screen door effect than they used to.
The third development in LCDs was the use of Micro-Lens Array (MLA) to boost the efficiency of light transmission through XGA-resolution LCD panels. Some XGA-class LCD projectors have this feature, but most do not. For those that do, MLA has the happy side effect of reducing pixel visibility a little bit as compared to an XGA LCD projector without MLA. On some projectors with this feature, the pixel grid can also be softened by placing the focus just a slight hair off perfect, a practice recommended for the display of quality video. This makes the pixels slightly indistinct without any noticeable compromise in video image sharpness. So visible pixel structure is diminished to the point where it almost as good as DLP, but not quite.
The Current State of the Art
The largest developers and manufacturers of LCD technology are Sony and Epson. These companies have no interest in standing by and letting Texas Instrument sweep the digital projector market with its competing DLP technology. So competition has driven both the LCD makers and Texas Instruments to improve their respective products in the ongoing battle for market share.
LCD technology has made notable improvements in contrast over earlier generation machines. The latest products from Sanyo and Sony demonstrate that LCD technology is fully capable of producing beautiful high-contrast video images. Nevertheless, DLP maintains its lead in contrast performance, while LCD projector makers have continued to emphasize latent advantages in colour fidelity and image sharpness for data display.
DLP colour has improved of late, and colour accuracy on the latest models is much better than it used to be. Sharp in particular has done some remarkable work in getting outstanding colour from DLP with its Z9000U home theatre product.
Both LCD and DLP are evolving rapidly to the benefit of the consumer. The race for miniaturization has produced smaller yet more powerful projectors than we might have even imagined possible just a couple of years ago. Light output per pound has increased dramatically. And video quality on the best LCD and DLP projectors now surpasses that available in a commercial movie theatre.
Projector Central continues to recommend both LCD and DLP projectors for a variety of applications. For mobile presentation it is hard to beat the current group of 3-pound DLPs on the market. However Epson's new 4.3 lb. machines, the Powerlite 720c and 730c, make it clear that LCD is still a very strong contender in the mobile presentation market. And for conference rooms that require higher light output and greater connectivity, LCD technology hold a commanding lead.
When it comes to home theatre, DLP has continued to make competitive advances in colour, contrast, and image stability that have served to establish DLP as the preferred technology for video. But the fact is that both DLP and LCD continue to improve, and both are capable of delivering higher quality video for home theatre than they ever were before.
Which technology is the best? Well, it all depends on your application--both technologies have advantages, and both have weaknesses. Neither one is perfect for everything. Understanding the differences between them will help you select the right solution for your particular needs.

1. DLP Technology:

DLP? projection is brighter, sharper and more reliable than alternative technologies.

The Digital Advantage: Brighter in Any Light
DLP? projection outshines analogue technologies because it brings more light from lamp to screen. The Digital Micro mirror Device at the heart of DLP? technology works more efficiently than the cathode ray tubes (CRT) and D-ILA systems found in many televisions. While these analogue technologies tend to lose a certain amount of light in transit, DLP? projection's greater efficiency creates exceptional brightness that increases with resolution, and does not degrade over time.

In home entertainment systems, DLP? technology produces a stunning show that plasma televisions and CRT televisions cannot match. And in the office, the superior brightness of DLP? projection gives presentations maximum impact-even in rooms where ambient light is difficult or impossible to control.

The Digital Advantage: Sharper at Any Size
Images and video displayed with DLP? projection's unique reflective technology appear seamless at any resolution. That's because the hundreds of thousands of mirrors making up the Digital Mirror Device in a DLP? projection system are spaced less than one micron apart, resulting in a 90% fill factor. Because the gaps between pixels are minimized, DLP? projection comes closer than any other technology to producing the exact mirror image of an incoming video or graphic signal.

2. Resolution:

Simply defined, "resolution" refers to the number of lines of picture image displayed on screen. The greater the resolution, the greater the picture quality. For example, a standard TV signal displayed on a standard TV set consists of 480 lines of resolution. HDTV (high-definition) signals, on the other hand, contain more than 700 lines -- hence their superior quality.

But, of course, there's much more to know about "resolution." And the more you know, the smarter your final choice will be when selecting the right home-theatre DLP? projector for you.

"Fixed" Resolution
DLP? projectors both come in different "fixed" resolutions. That is, not every projector has the same resolution as every other. And a projector's fixed resolution rarely matches the exact resolution of the incoming signal. Therefore, the projector must first resize the signal's image internally, through shrinking or stretching, to map it onto its own fixed-resolution DLP? panel.

Standard and Widescreen formats:

A DLP? Projector Panels' 4 Format Ratio
As you can see, (almost) all of the DLP? projector fixed resolutions are in a 4 ratio format (horizontal:vertical). That is, the projector's internal panel, onto which the incoming image must be mapped, is a bit wider (by 1.33 times) than it is high. This is the industry standard for most portable home-theatre DLP? projectors.

Projecting a Standard TV Broadcast
This 4 ratio/shape is exactly the same as a standard TV signal (NTSC) and picture tube. An incoming standard TV video signal consists of 480 lines of resolution (and is 640 pixels wide). When displaying a standard TV broadcast with a DLP? projector, the incoming image will first be expanded so that it corresponds/maps to the resolution of the projector's internal panel (either exactly 800 pixels wide x 600 pixels/lines in height if SVGA, or 1024 x 768 if XGA). And, as previously mentioned, a mathematical algorithm is used to add/interpolate pixels within the expanded image, so that the density of pixels will remain the same as the original signal. The resulting image, when projected, will completely fill the 4 ratio screen top-to-bottom and left-to-right, regardless of its size, with a bright, dynamic picture.

True "Home Theatre" and its 16:9 Format Ratio
True "Home Theatre" signals mimic the shape of a movie theatre screen rather than a standard TV. That is, the ratio of width to height is much more exaggerated, in a ratio of 16:9 (1.78 times wider than high) rather than 4 (1.33).

For example, high-definition television (HDTV) comes in two different formats, both of which are in a 16:9 ratio: 720p (720 lines of resolution in "Progressive" scan format) and 1080i (1080 lines in "Interlaced" format). There is currently no HDTV standard, and the various broadcasting companies are currently using one or the other system. (We will discuss "Progressive" vs. "Interlaced" scans shortly.)

How a 4 XGA DLP? Projector Handles an Incoming 16:9 Signal
Over the next several years, the current NTSC television standard will be replaced with the HDTV standard. As alluded to above, a wide-screen video signal (with a 16:9 ratio horiz:vert) cannot be mapped onto a projector's internal panel whose dimensions are in a 4 ratio. Nor will the incoming signal's resolution (in terms of lines) exactly match the projector's "fixed" resolution. The following two scenarios help explain how these situations are resolved:

Scenario 1:
Suppose you have a DLP? projector containing an XGA panel (1024 pixels wide x 768 pixels/lines of resolution, a 4 ratio horiz:vert), with an incoming HDTV video signal (1280 pixels wide x 720 pixels/lines of resolution, a 16:9 ratio). When the incoming image is mapped onto the projector's internal panel, it needs to first be "shrunken" by 20% so that the original 1280-pixel-wide HDTV image will fit onto the 1024-pixel-wide XGA panel. The proportional 20% shrinkage in the vertical dimension will result in an image that no longer contains 768 lines of resolution, but rather 575. This necessary loss of resolution occurs in spite of the fact that an XGA panel has the capacity for 768 lines of resolution, and an HDTV signal consists of "only" 720 lines. But the final picture, when projected onto the big screen, will still look great -- far superior to standard TV's 480 lines.

Also note that because the resulting 575-line image is less than the DLP? projector's internal panel's 768-line capacity, only 80% of the panel's vertical dimension will be covered with image, and the rest will be blank. Therefore, when centred and projected onto a 4:3-ratio screen, the resulting picture will have the so-called "letterbox" effect, with dark horizontal bars visible both above and below the image*.

*Some projectors will project black in the blank area, while others will actually turn off the pixels for darker black area.

Scenario 2:
Take same projector with an XGA panel, and an incoming DVD video signal. DVD uses the NTSC standard (640 pixels wide x 480 pixels/lines of resolution, a 4 ratio) so that discs can be fully viewed on standard television sets. However, most DVDs are also "enhanced for 16:9," meaning that they contain an additional encoded 16:9 image consisting of the same number of lines of resolution (480) but extending across a full 854 pixels horizontally. Therefore there is no loss of resolution when viewed on an XGA home-theatre projector.

When this 16:9 image is mapped onto the XGA projector's internal panel (which can accommodate a line as wide as 1024 pixels), the full image can be accommodated without first having to be "shrunken." (In fact, in this case, it will be "stretched" by about 10% so that the 854-pixel-wide signal will fill the 1024-pixel-wide panel. The corresponding 10% stretch in the vertical dimension increases the image to about 575 lines high, still less than the panel's 768-line capacity, thus resulting in a "letterbox" effect.) Since there is no loss of resolution, the projected picture will be of stunning quality.

Will an SVGA DLP? Projector Do as Well as an XGA?
What about those very inexpensive SVGA DLP? projectors? Well, if you want to enjoy HDTV, don't even consider one. Because of its much lower-resolution 800 x 600 internal panel (as compared to an XGA projector's 1024 x 76 the final picture will contain even less resolution than a standard NTSC TV signal! This is because, when an incoming 720p or 1080i HDTV wide-screen image is mapped onto the projector's panel, it needs to first be "shrunken" by 37.5% (if 720p) or 41.7% (if 1080i), so that the original 1280-pixel-wide HDTV image (if 720p) or 1920-pixel-wide image (if 1080i) will fit onto the 800-pixel-wide SVGA panel. The proportional percentage shrinkage in the vertical dimension results, in either case, in an image that no longer contains 720 or 1080 lines of resolution, but rather 450, which is less than standard TV's 480 lines!

Line Doublers

Unlike TV picture tubes and computer monitors, DLP? projectors don't actually "draw" the picture. Rather, at any given split-second in time they are either projecting image or not (i.e., the pixels are either "on" or "off"). Thus, an attempt to project an "interlaced" signal would result in every other line (the "odd" lines) being projected by themselves for 1/60 of a second, followed by just the even lines, resulting in a picture worse than any big screen TV.

To accommodate incoming interlaced signals such as from a TV broadcast (incl. cable), VCR, DVD or laserdisc, most projectors contain deinterlacer or "Line Doubler" circuitry that changes the interlaced signal into a progressive EDTV format. This is accomplished by waiting a full 1/30 of a second to receive both the odd and even lines before projecting them together onto the screen. During this split-second wait, the previous image frame continues to be projected a second time, so there is a fully formed image being displayed at all times.

Despite its name, there is not actually a "doubling" in the number of lines of resolution. But there is a doubling of the amount of time that each image frame is displayed, resulting in a picture that not only is devoid of "flicker," but which is also brighter.

With a high-quality line-doubler (and not all of them are), the resulting picture quality from an "interlaced" source is absolutely superb.

WHAT IS HDTV (High Definition TV)?

HDTV is a type of television signal, which is scheduled by government mandate to replace the current US standard, NTSC, by the year 2006. HDTV is different from NTSC in several ways. First, HDTV is broadcast in the 16:9 aspect ratio as compared NTSC's 4 aspect ratio. Second, HDTV resolutions are increased from (if expressed in computer resolution terms) 640 x 480 to either 1922 x 1080 (or 1080i) or 1280 x 720 (or 720p). Thirdly, because the signal itself is digital rather than analogue, it can carry a lot of information, including full digital audio with multiple channels.

The most important piece of information that relates to HDTV is that you should not buy an SVGA resolution projector if you want to watch HDTV quality signals. An SVGA will actually give you about the same resolution as a regular NTSC TV set because of issues with mapping the image. However, an XGA resolution projector will more closely match the HDTV signal, making for an image far better than an NTSC set.

RCA, or Composite, Cables
These are the most common cables, used to hook up your standard VCR and stereo equipment. Typically, they are colour-coded: red, white, and yellow. Red is for right channel audio. White is for left channel audio. Yellow is for video. The entire video signal is transmitted by one cable. This is the lowest quality cable for a video source, but again, it is also the most common. Most new televisions, all video camcorders, all VCRs, and all videodisc players will have RCA jacks for these cables.

S-video, or Y/C, Cables
This cable might also be referred to as a SVHS cable and can be found on most high-end televisions, all videodisc players, camcorders, digital cable and satellite set top boxes, and SVHS VCRs. S-video cables differ from composite cables in that they split video signal into two different components: luminance and chrominance. The S-video cable will offer marked improvement over a composite cable.

Component Cables
Component cables look just like composite cables. The difference is that, where a composite cable carries the entire video signal on a single cable, component cables split the signal in three. This connection gives a superior image over composite or S-video connections. The signal itself is referred to as either Y,Cr,Cb, or Y,Pb,Pr. Most manufacturers make connecting these cables easy by colour coordinating them. The tips of the cables and jacks will be red, green and blue. Unfortunately, this can be a bit confusing because computer RGB connections are coloured the same way. A good rule of thumb is that, if the connections are RCA type, it is usually a component cable. Most high-end DVD players and HDTV tuners will have component connections.

Portable DLP? Projectors and Component Cables
Portable DLP? projectors usually have very little space for connections. Due to the space restriction, many have the 15-pin VGA connection double as the component connection as well. The projector will use the same three pins out of the fifteen-pin connector for component video that it uses for its RGB computer connections. The projector is designed to detect the type of signal it receives and process it accordingly. If you need a component cable for one of these projectors, you should order a cable that has a 15-pin connector on one side, and three RCA connectors on the other. Some larger projectors have separate component connections. Consult the spec sheets.

VGA Cables
This is your standard monitor cable. It is typically male-to-male with three rows, 15 pins. A VGA cable is used for computer to monitor, or computer to projector connections. Its only home theatre application may be as a connection to an HDTV decoder, such as the current RCA model.

DVI cables
Digital Video Interface (DVI) cables look a little like a standard VGA cable, but they are slightly larger. Under ideal circumstances, the DVI cable creates a ?digital to digital? connection between video or data source and display device. There are, however, only limited situations when this ideal circumstance occurs.

DVI is still developing, so there is no universal standard for the DVI cable as of yet. Currently projector manufacturers including InFocus, Sony, and Epson use different standards. Look for DVI to grow in popularity and become standardized over the next couple of years.

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