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The Advantages and Limitations of LCD Technology

Limitations and Weaknesses of LCD Technology

LCD Panels have Unknown Lifespans

With extended exposure to extreme heat levels and high intensity UV [Ultraviolet] light, the organic compounds used to make most LCD panels can be expected to degrade over time. This could lead to a reduction in contrast and a discoloration of the projected image. The only fix would be to replace the panel. This can be extremely expensive, and you are usually better off replacing the entire projector.

So, the question on people’s minds is, how long will the panels last? There is no data available on this. No independent labs have tested and compiled data on this subject for general consumption. LCD manufacturers do not usually acknowledge that degradation can happen, so they make no representations regarding the expected lifespan of LCD panels. They claim, probably rightly, that any degradation that occurs would start to become a problem beyond the practical lifetime of the projector as a whole.

It has been suggested by a trusted source in the industry that produces projectors with both DLP and LCD technology, that LCD panels can be expected to last from 4,000 hours to 10,000 hours, depending on the projector’s level of
brightness. Quicker degradation can be expected from the brightest LCD light cannons which place more stress on the panels. Home theater projectors are typically less bright, and these are expected to have a longer lifespan.

Over the past several years, Texas Instruments have run some tests on LCD lifespan. They claim that their tests show that LCD panels will degrade much more quickly than LCD vendors would like us to believe – and they will certainly
last for less than the 4,000 hours mentioned above. These test results are not accepted by the LCD vendors because the tests were performed running the projectors continuously 24 hours a day, 7 days a week, for months on end. Epson and 3LCD point out that the models tested by Texas Instruments were never designed to be used this way, so the results are no indication of what normal consumers can expect.

The introduction of inorganic LCD panels adds a new dimension to this issue. In theory, inorganic panels should not suffer from the same degradation as traditional organic panels, due to the fact that they do not contain the organic compounds found in organic panels that fail under UV light and intense heat. LCD vendors do not even discuss the issue of panel degradation, so they have nothing to say about the expected lifespan of inorganic panels. Nor has Texas Instruments made any claims about inorganic panel life expectancy.

Dust Spots

Because LCD light engines are unsealed, particles of dust can settle on the LCD panels, which can result in indistinct, vague spots appearing on the projected image. This is not too much of a problem when projecting static images like a
still photograph, or a chart. But in HT systems it can be quite distracting when a stationary spot appears in the middle of a moving picture.

Dust particles in the blue or red channels of an LCD are not usually visible enough to cause a problem. But particles in the green channel are much more conspicuous and can be extremely distracting. Some manufacturers have taken steps to void the necessity of shipping the unit back for cleaning and removal of dust. Sanyo’s HT models, for example, come with a hand pump that will send a jet of air over the panels and remove dust particles.

LCD vendors point out that air filter systems are much more reliable these days than in the past, and, provided the filters are cleaned and replaced at regular intervals, dust contamination can be largely eradicated. However, most users
neglect to follow the manufacturers’ recommendations and forget to clean the filters, which will increase the risk of dust contamination. By the way, most manufacturers cover dust removal under warranty, so it makes sense to consider
buying an LCD projector with an extended warranty.

Lower Contrast Ratings in Business Projectors

Typically, education and commercial LCD projectors use the less expensive organic panels and do not incorporate auto iris technology. For these reasons, they have relatively low contrast ratings – normally from 400:1 to 700:1. By contrast, DLP models in the same lumen, price and resolution class often achieve contrast ratings of 2000:1 or more.

Actually, this isn’t really a technical disadvantage – it just looks bad on paper. Most business and classroom presentations are given with the room lights on. Schoolchildren will need to be able to take notes. With a moderate level of ambient light, the contrast rating of your projector is pretty much irrelevant. With moderate ambient light the effective contrast level on screen will be around 50:1, regardless of the projector’s theoretical rating. It is certainly a marketing disadvantage for LCD vendors – buyers who are not aware of the impact of ambient light will assume DLP models are more desirable because of their higher contrast specs.

Advantages of LCD Technology

Price Advantage in Home Theater Market

In the HT [Home Theater] market, LCD [Liquid Crystal Display] technology has a clear advantage over DLP [Digital Light Processing] in the sense that LCD technology is inherently cheaper than DLP. This means that buck for buck, LCD
projectors, particularly in the 1080p market, will deliver outstanding picture quality for what you pay. Also, they usually have extra features that are lacking in their DLP counterparts.

This price advantage only applies in the home theater market – with business projectors designed for presentations and use in conference rooms there is no great price difference. This is because DLP manufacturers can use cheaper 2x
color wheels in business models – they do not require the high speed wheels and all the associated electronics that are necessary to display movies in a home theater setup.

Fewer Artifacts

Rainbow artifacts and dithering artifacts appear only on single-chip DLP models. Since they do not occur at all with 3LCD projectors, it’s not uncommon to perceive a more stable image when doing a side-by-side comparison between an LCD and DLP projector of the same cost and similar technical specifications. LCD video imaging can appear to be cleaner and have less noise.

Better Contrast

Many home theater LCD projectors achieve deeper blacks and better overall contrast than their DLP equivalents. This is especially true for LCD projectors using auto iris technology and inorganic LCD panels. It is more expensive to produce inorganic panels, so they are not used in commercial projector models. The reason inorganic panels achieve greater contrast is that the liquid crystals’ resting position is closed [black] and voltage is needed to open them. With traditional organic panels, the opposite applies: the resting position is open [maximum brightness] and voltage is required to close the crystals. This built-in contrast advantage of inorganic panels has made LCD extremely competitive in the home theater market. There has been a significant improvement in ANSI [American National Standards Institute] contrast in particular. In independent testing, LCD projectors with organic panels achieve around 250:1 ANSI contrast. Their inorganic cousins achieve far higher levels around 400:1 to 450:1.

Auto Iris Systems

LCD manufacturers have been actively developing auto iris systems that give the viewer a perceived incremental contrast improvement on the display. There is no technical reason that the same thing can’t be done with DLP systems. But DLP
home theater projectors are already at a cost disadvantage, and adding auto iris technology would drive the cost even higher. DLP vendors also seem to believe that DLP contrast is sufficient, and extra enhancement is not required. For
whatever reason, DLP vendors are dragging their feet about introducing auto iris technology into their HT products.

Sharper Display at Low Resolutions

In LCD projectors, the pixel structure is more sharply defined than in DLP models. This results in a sharper image, particularly at low resolutions where the pixels are effectively bigger. It applies particularly to data display in low resolution business projectors displaying SVGA [Super Video Graphics Array, 800 x 600 pixels] and XGA [Extended Graphics Array, 1024 x 768 pixels], especially when displaying data like charts or still images. At these low resolutions the screendoor effect associated with LCD technology is most prevalent, but the sharper pixel definition can also give a sharper display of data images. Low resolution DLP projectors by comparison can look a bit soft when displaying data.

At higher resolutions, the difference in perceived sharpness in minimal, and with 1080p projectors it is not an issue at all. Extremely sharp pictures are achieved by both technologies at this high resolution. At 1080p, any difference in sharpness is probably due to factors other than the display technology, such as video processing and the quality of the lens.

Higher Installation Flexibility

Home theater LCD models usually come with extensive horizontal and vertical lens shift, and a 2.0x zoom lens. For this reason, they are easy to install pretty much anywhere you want. Many people opt to install them on a rear shelf at the
back of the room. DLP projectors, by contrast, usually have little or no lens shift and short zoom lenses. The projection geometry is limited by the fixed throw angle, and often there is only one optimal position for a DLP projector at any given location and screen size.

All this makes the lens flexibility of LCD projectors very appealing to the DIY home theater enthusiast with a limited budget. Most DLP projectors end up being mounted on the ceiling, and this is not necessary with LCD models. With LCD you don’t have the additional cost of a ceiling mount and long video cables, or the hassle of running cables through the ceiling and walls, or having an ugly length of cabling along the ceiling.

Higher Power Efficiency

LCD projectors are inherently more power efficient than their DLP counterparts. Commonly, DLP models require higher wattage lamps to achieve the same display brightness as LCD projectors. This is particularly true when you compare LCD
models to DLP models which have no clear segment in their color wheels. For example, if you look at two 1080p projectors on the market – the Sharp Z15000 requires a 250-watt DLP projector lamp to achieve an ANSI lumens level of 1600.
The Panasonic AE3000 achieves the same 1600 ANSI lumens level with a 165-watt LCD projector lamp. This makes for a significant difference in power consumption. The DLP model will also generate more heat in the projector room.

The above information should help you to make an informed decision as to whether to opt for LCD or DLP technology, whether you are interested in the business or home theater projector market. However much care you take of your projector, the bulb has a finite life, and you will eventually need to think about a source of cheap projector lamps. The good news is, a replacement projector lamp can be found easily on the Internet. LaptopsForLess.com carries a comprehensive range of replacement bulbs which are compatible with all the major projector brands and models. What’s more, you will make a considerable cost saving compared to buying the manufacturer’s own brand replacement lamp.