Projectors: LCD Verses DLP (The downfall of DLP technology)
The most common question heard when purchasing a new projector for the home, office, or classroom is: should I get an LCD projector or a DLP projector? LCD, which stands for ‘liquid crystal device’ and DLP, short for ‘digital light processing’ are the two most popular projector imaging technologies. With so many different brands and different types available, it can be confusing for the buyer to make a decision between both technologies. The fact is that LCD projectors offer far better image quality and colour accuracy. The next paragraph tells you why DLP projectors struggle with reproducing an equal rate of image quality.
Imagine a set of blinds in your room for your bedroom window. By a twist of a rod you can make the shutters open or closed, according to whether you want to let light in or not. And such is exactly how an LCD projector functions. Each pixel operates like a single shutter on a set of blinds to either allow light through or to block it. DLP on the other hand is formed of millions of microscopic mirrors or ‘pixel elements’ as the professionals like to call them. Each pixel element functions to either reflect light or block it.
How the light source is processed from the point at which the projector turns on to when the picture reaches your screen is vitally significant for image quality, brightness and colour accuracy. LCD projectors project white light from the lamp by separating it into red, blue and green components, by three mirrors which transfer the coloured light to 3 different LCD panels. The 3 LCD panels create the elements of the image by switching each pixel on and off. The pixels are then combined in a glass prism to send the projector image. Something important to understad about LCD projectors is that all three colours are projected onto your projected surface at the same time. The way a DLP projector runs is very different and even the way an image shows up is not the same. With DLP, white light from the lamp is sent through a turning colour wheel with transparent red, blue and green segments, at speeds up to 11,000 rpm/s. This approach to projecting an image casts a sequence of red, blue and green light. The millions of micro mirrors as mentioned above reflect the coloured light on the pixels to produce the image elements. The elements of the image are displayed in sequence on the screen, one colour at a time. The viewer’s vision will then put together each coloured element of the image into a whole image. From LCD projectors, all colours are available all the time to create the highest brightness and spectacular colour accuracy. In DLP, only one colour is available at once, and so resulting in lower colour brightness and accuracy. Some DLP manufacturers have put a white segment into the colour wheel to improve general brightness, but this then damages colour accuracy.
I read in forums all the time that DLP gives a higher contrast ratio and as such must be superior. For those unaware, the contrast ratio is a measure of a display system defined as the ratio of the luminance of the brightest white to that of the darkest black that the system is capable of producing. DLP projectors do provide high contrast specifications when compared to a majority of LCD projectors. At one glance, this can seem to be a plus, however, in the real world, the true black level is determined by the ambient light in the room when the projector is being used. Do not be fooled by contrast specifications on websites and in brochures.
When the content you plan to see has moving images, DLP projection technology also creates image errors, or ‘artifacts’. The most common artifact that a DLP projector forms with moving images is colour break up. Colour break up is incontrovertible in DLP systems because moving images change between the time red, blue and green colours are displayed. LCD projectors do not have this downside because all the colours are processed at once. DLP manufacturers have formed 3DLP solutions using 3 chips to resolve the colour break up artifacts, but the price tag of these projectors make them almost impossible for the majority of businesses and consumers.
Another difference between LCD and DLP is how they balance for the refractive qualities of light. Take yourself back to high school science, and recall when they taught you how the various colours of light refract differing amounts when directed through the same lens. The disadvantage with DLP projectors is that they use the one same panel for the same lens to project Red, Blue and Green. All 3 colours are obviously different and refract light in different ways. Usually with a DLP projector, some extra yellow colour will come up above and some blue will come through below an image containing something as simple as a straight black line. During manufacturing LCD projectors can be fixed to minimize these effects on the projected image, because each colour is directed on separate LCD panels.
The isolated veritable plus (excluding price) with buying a DLP projector is its smaller overall size and weight. However, this is only relevant to portability and needs to be traded off against the image plusses of LCD projectors. If overall picture quality is important to you, then the choice is a no-brainer. Choose an LCD projector! LCD projectors will definitely produce bright, colourful images with fewer image mistakes. If you desire to learn more about LCD technology in more detail, see this spectacular resource website: Explore 3LCD. If you have any other questions, go to Projector Central and send me an email.
Jonathan King is the sales and marketing manager at Projector Central, Australia’s number one online shop for projectors. Brisbane based, Projector Central has been servicing Australia for 15 years. For data projectors in the Gold Coast and Interactive Whiteboards, contact Projector Central today.
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