Projectors: LCD Verses DLP (The downfall of DLP technology)
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The typical question heard when purchasing a new projector for the home, office, or classroom is: would I get an LCD projector or a DLP projector? LCD, short for ‘liquid crystal device’ and DLP, short for ‘digital light processing’ are the two most common projector imaging technologies. With so many business brands and different models available, it can be challenging for consumers to choose between these technologies. Ultimately LCD projectors provide far better image quality and colour accuracy. The next part of this article will explain why DLP projectors struggle with reproducing the same standard of image quality.
It’s like a set of blinds in your household on your bedroom window. By a twist of a rod you can turn the shutters open or closed, depending on whether you want to let light in or not. That is exactly how an LCD projector operates. Each pixel operates like a unique shutter on a set of blinds to either send light through or to block it. DLP on the other hand is formed of millions of microscopic mirrors or ‘pixel elements’ as experts like to call them. Each pixel element operates to either reflect light or block it.
How the light source is processed from when the projector is turned on to when the image reaches your screen is extremely significant for image quality, brightness and colour accuracy. LCD projectors process white light from the lamp by splitting it into red, blue and green components, by three mirrors which project the coloured light to 3 different LCD panels. The 3 LCD panels form the elements of the image by switching each pixel on and off. The pixels are then meshed in a glass prism to deliver the projector image. A significant point to know about LCD projectors is that all three colours are sent onto your screen all at the same time. The way a DLP projector works is totally different and even the produced image appears is not the same. With DLP, white light from the lamp is projected through a rotating colour wheel with transparent red, blue and green segments, at speeds up to 11,000 rpm/s. This approach to forming an image requires a sequence of red, blue and green light. The millions of micro mirrors as described above reflect the coloured light on the pixels to construct the image elements. The elements of the image are sent in sequence on the screen, one colour at a time. The viewer’s vision will then combine each coloured element of the image into a single full image. From LCD projectors, all colours are available all the time to deliver the best brightness and great colour accuracy. In DLP, just one colour is available at once, and so causing lower colour brightness and accuracy. Some manufacturers have included a white segment into the colour wheel to improve brightness overall, but this goes and detracts from colour accuracy.
I hear in forums all the time that DLP provides a higher contrast ratio and ergo must be superior. For those who are uncertain, 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 machine is capable of. DLP projectors do offer high contrast specifications when compared to the majority of LCD projectors. At a glance, this can seem to be an advantage, however, in reality, the true black level is determined by the ambient light in the room when the projector is used. Do not be tricked by contrast specifications on websites and in brochures.
When the content you are trying to bring to life needs moving images, DLP projection technology can also have image imperfections, or ‘artifacts’. The most often seen artifact that a DLP projector shows with moving images is colour break up. Colour break up is inherent in DLP systems because moving images change between the time red, blue and green colours are pulled up. LCD projectors do not have this downside because all the colours are sent at the same time. DLP designers 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 many businesses and consumers.
Another differentiation between LCD and DLP is how they compensate for the refractive qualities of light. Remember back to high school science, and recall when they taught you how the various colours of light refract varied amounts when projected through the same lens. The downside with DLP projectors is that they take the one same panel and the same lens to project Red, Blue and Green. All 3 colours are not the same and refract light at different levels. Generally with a DLP projector, an extra yellow colour will come up above and a superfluous blue will show below something as simple as a single black line. In building LCD projectors can be adapted to take away these effects on the projected image, because each colour is processed on a separate LCD panels.
The sole real plus (excluding price) with choosing a DLP projector is its smaller total size and weight. However, this is only relevant in regard to transport and must be traded off against the image benefits of LCD projectors. If the result of the picture quality is vital to you, then the solution is no-brainer. Go for an LCD projector! LCD projectors will always make bright, colourful images with fewer image imperfections. If you need to find out more about LCD technology in more detail, have a gander at this fantastic resource website: Explore 3LCD. If you have any more questions, jump onto Projector Central and send me an email.
Jonathan King is the sales and marketing manager at Projector Central, Australia’s premier online store for projectors. Brisbane-based, Projector Central has serviced Australia for 15 years. For data projectors in the Gold Coast and Interactive Whiteboards, contact Projector Central today.
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