Q. What are the differences between the various display technologies available on the market today? Besides brightness and picture quality, what else should I be looking out for? How do I make the right buying decision?
A. Until recently, there were only two options for thin displays: LCD (liquid crystal display) and plasma. Today, a newer technology called Ultra-Thin MicroDisplay (UTMD) is heating up the competition to provide a reliable display that not only offers excellent image performance but is affordable and available in a thin-form factor.
Let's consider the merits of the technology contenders:
Liquid Crystal Display (LCD)
Today, LCD monitors and televisions are quite common in the 30-inch and smaller category, and sizes as large as 46 inches are becoming prevalent. LCD displays have become increasingly popular as makers have found new manufacturing efficiencies and have brought prices down significantly in recent years. Buyers of LCDs like their thin industrial design and light power consumption.
However, like any technology, LCD has some drawbacks. The overall color space that an LCD can create is limited and less dynamic than other technologies such as CRT (cathode ray tube). The image quality is negatively affected especially when the images change quickly and when viewed at an angle. In general, LCDs have trouble showing true blacks, negatively affecting their contrast ratios (the measurement of the difference between light and dark). Over time, LCD displays slowly become less bright, and while an LCD display’s backlights tend to last a long time (about 50,000 hours to the point where they are about half their original brightness), it is generally not cost effective to ever replace the backlight. Thus, LCDs simply wear out over time.
LCDs also are limited in their diagonal image size. LCD panels are created in hugely expensive fabrication plants. But, once up and running, these fabs can create panels quite efficiently. This, in combination with market forces, has led to dramatic price declines in recent years for LCD monitors and televisions. However, the upfront manufacturing costs make it challenging for LCD makers to scale displays to larger sizes. Therefore, the largest cost effective LCDs today are only about 46 inches. Inch for inch, LCDs are the most expensive of the three technologies described here.
PDPs pixel response is much faster than LCDs. They can create very nice black or dark images since when the pixels are turned off, the light goes away completely (unlike LCDs). The color gamut for a PDP is also generally better than an LCD. In addition, PDPs typically look better when viewed at an angle than an LCD. On the other hand, one of the major drawbacks with plasma has been the fixed life expectancy. Like LCDs, PDPs become less bright over time. PDPs are also susceptible to burn-in, meaning that if you hold a static image on a PDP for a period of time, that image can become permanently fixed on the display. For example, the CNN logo that remains at the bottom of screen--with plasma, that logo might still be there after you turn the channel. PDP displays perform best in darkrooms, but ambient light can greatly reduce the contrast and image quality of the display. Other drawbacks are that it emits heat, requires a good deal of electricity, and usually offer lower resolution than competing technologies. In addition, they can be quite heavy while they are thin.
Ultra-Thin MicroDisplay (UTMD)
The newest technology to the thin marketplace is a novel approach to an existing technology. Ultra-Thin MicroDisplay (UTMD) takes all of the inherent image quality advantages of MicroDisplay rear projection and applies a completely new thin optics technology. The result is a MicroDisplay that is only 7 inches deep, compared to 17 inches for the traditional depth of rear projection. While these displays are referred to as MicroDisplay, there is nothing "micro" about the image. Rather, given its history from large front projection, the created image from a UTMD device can be quite large--up to about 70 inches. Moreover, since the core technology is projection, a good deal of space within the display is actually air, making UTMD more cost competitive and lighter than PDP or LCD at similar sizes. In terms of life expectancy, unlike PDP or LCD, the user gets the same image quality and brightness as the day it left the factory by replacing the lamp on the UTMD device.
So, which is best? Consider these decision-making criteria:
1. Form fits function
Before you can determine which display technology is best, you first need to critically examine its intended purpose. A 40-inch LCD is not the best for a 40-ft by 30-ft boardroom. There are at least two broad areas where these large area thin digital displays are popular: office and public spaces. In the office, large thin displays are becoming more and more prevalent, in areas where front projection is not feasible or to support additional data needs for situations like video conferencing. The size of the venue is one of the primary drivers for which display is best. In smaller conference rooms or lobbies, 40-inch LCDs are quite common due to its life expectancy compared to plasma. In larger conference rooms, UTMD is probably the better choice, because the image brightness can be renewed with a new bulb and the larger image size.
In public spaces, thin displays are increasingly used as advertisers compete for the attention of consumers who are increasingly immuned to messaging. Here, the absolute size of the image is critical. Again, UTMD seems to be the logical choice given its size and cost advantages.
After considering the pros and cons, it comes down to the picture on the screen. Several different things frame image quality: contrast, color gamut, fast motion video quality, brightness and viewing angles, just to name a few. It does not come down to a single specification such as brightness; rather, it is a complex matrix of these different factors. One of the primary drivers of image quality is black level, or simply how black is black. Black level also affects how deep colours are represented. No display can create true black, but some do much better than others do. The older CRT technology actually does a great job of creating good black levels. The next best technology for creating good black levels is UTMD devices. Black level is a challenge for LCD and Plasma. Color gamut is another critical driver of image performance. To produce great and accurate images, the color gamut on the display needs to be wide enough to create the complete palette of colors and it needs to match closely with industry standards. Again, UTMD has the advantage in this specification, with plasma close behind.
Brightness is usually pointed to the most as a driver of image quality, but in general, all of these displays create enough image brightness to be viewed comfortably in rooms with average ambient light. In general, LCD devices have the highest brightness specifications, and thus perform best in spaces with bright ambient light. Ironically, there is some concern that some of these displays are getting too bright for some applications. One ergonomics group is already asking desktop LCD monitor makers to lower brightness in their offerings.
Image quality is quite subjective. Some describe LCD displays as cold and digital, while others may describe the same display as bright and sharp. If possible, all three competing technologies should be viewed and evaluated in an environment very similar to where the display will be used. In a smaller room with a lot of ambient light, an LCD might provide the best image experience, whereas in a larger room with an average amount of light, a UTMD device will probably perform better.
Total cost of ownership
Although prices are steadily falling on these large displays, they still represent a significant investment. Beyond simply the initial outlay of cash for the display, buyers should be cognizant of the total cost surrounding the display. Factors that affect the total cost of ownership for these displays include factors such as electricity, integration, reliability, lifespan and replacement cost. There is actually a large difference in the amount of electricity used by these different display technologies. For example, looking at 61-inch plasma and UTMD displays, an average 61-inch plasma display consumes about 600 watts per hour, whereas an average UTMD consumes about 230. Assuming heavy use of both displays, the annual difference in electricity costs could be as high as US$100. Multiply that by the expected lifespan of both, and you are looking at spending more than US$500 on electricity for the plasma unit versus UTMD.
Integration and installation can also be a significant expense. Factors that can increase the cost of installation include weight and the ruggedness of the display. A 150-pound plasma display will cost more to attach to a wall than a 50-pound LCD. One of the complaints with plasma has been how fragile they can be. In a rollout of a large number of plasma displays across a corporation, it is conceivable that a number of these could be damaged and fail before they are even installed.
Of course, the lifespan of the display will be a major driver of the total cost of ownership. As mentioned before, with both LCD and plasma displays, the brightness of each slowly diminishes over time until the unit fails. LCD brightness tends to last longer than plasma. The only thin display technology that has renewable brightness is UTMD. Of course, the user should budget for the cost of a lamp replacement every four to five thousand hours, but after replacing the bulb, the brightness of the display goes back to where it was when it came out of the factory.
Our expert: Wee Yep Yin, marketing manager for Asia-Pacific at InFocus.