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. 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 RM30,000*, there is only one chip. In order to define color, there is a color wheel that consists of red, green, blue, and sometimes white filters. This wheel spins between the lamp and the DLP chip and alternates the color of the light hitting the chip from red to green to blue. The mirrors turn on and off based upon how much of each color 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 color channel individually. In LCD projectors with good controls on board, this can enable the projector to achieve very good, and sometimes excellent color fidelity. In most single-chip DLP projectors, color is fixed and defined to a large degree by the physical color wheel and the color temperature of the lamp, which changes over its usable life. So while DLP technology has gotten much better at reproducing accurate color, 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 mini-projectors 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 theater world primarily due to two video quality advantages—better contrast and the lack of pixelation. 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 gray 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 theater 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 pixelation 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 theater enthusiasts (quite understandably) because of this flaw in the image.
DLP technology went a long way toward eliminating the screen-door effect. In SVGA (800×600) 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 theater 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 (1,024×768). 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 more dense and less visible. In XGA resolution, DLP projectors have an invisible pixel grid on any typical home theater screen no matter how big. LCD projectors with standard XGA panels still have a visible, but much reduced screendoor 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 screendoor 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 Epson and Sony demontrate 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 color fidelity and image sharpness for data display.
DLP color has improved of late, and color accuracy on the latest models is much better than it used to be. Sharp in particular has done some remarkable work in getting outstanding color from DLP.
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 theater.
When it comes to home theater, DLP has continued to make competitive advances in color, 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 theater 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.