Projectors: LCD Verses DLP (The downfall of DLP technology)
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The typical question that is asked when looking for a new projector for the home, office, or classroom is: will I buy an LCD projector or a DLP projector? LCD, standing for ‘liquid crystal device’ and DLP, which stands for ‘digital light processing’ are the two most common projector imaging technologies. With so many business brands and different models available, it can be overwhelming for the buyer to make a choice between both technologies. The fact is that LCD projectors offer better image quality and colour accuracy. The article below explains why DLP projectors struggle with reproducing a similar standard of image quality.
Visualise a set of blinds in your home over your bedroom window. By twisting a rod you can make the shutters open or closed, depending on whether you want to let light in or not. This is exactly how an LCD projector works. Each pixel functions like its own shutter on a set of blinds to either shine light through or to block it. DLP on the other hand is formed of millions of microscopic mirrors or ‘pixel elements’ as the experts like to call them. Each pixel element operates to either reflect light or block it.
How the light source is processed from the point when the projector turns on to when the image reaches your screen is ultimately significant with regard to image quality, brightness and colour accuracy. LCD projectors shine white light from the lamp by cutting it into red, blue and green components, by three mirrors which transfer the coloured light to 3 individual LCD panels. The 3 LCD panels make the elements of the image by turning each pixel on and off. The pixels are then projected in a glass prism to deliver the projector image. An important point to understad about LCD projectors is that all three colours are projected onto your wall at the same time. The way a DLP projector functions is widely different and even the way an image appears 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 method of forming an image forms a sequence of red, blue and green light. The millions of micro mirrors as mentioned above reflect the coloured light on the pixels to create the image elements. The elements of the image are projected in sequence on the screen, one colour at a time. The viewer’s eyes will then put together each coloured element of the image into the single total image. With LCD projectors, all colours are available all the time to form top brightness and fantastic colour accuracy. In DLP, only one colour is available at once, and so resulting in lower colour brightness and accuracy. Some developers have included a white segment into the colour wheel to improve general brightness, but this goes and degrades colour accuracy.
I see in forums all the time that DLP offers a higher contrast ratio and ergo must be superior quality. 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 machine is capable of producing. DLP projectors do provide high contrast specifications compared to most LCD projectors. At a glance, this seems to be a plus, however, in reality, the true black level is determined by the ambient light in the room when the projector is being used. Do not be tricked by contrast specifications on websites and in brochures.
When the content you plan to view requires moving images, DLP projection technology can also create image marks, or ‘artifacts’. The most commonplace artifact that a DLP projector displays with moving images is colour break up. Colour break up is to be expected in DLP systems because moving images change between the time red, blue and green colours are shone. LCD projectors do not have this disadvantage because the colours are sent simultaneously. DLP manufacturers have developed 3DLP solutions using 3 chips to answer the colour break up problem, but the expense of these projectors make them hardly practical for the large part of businesses and consumers.
Another difference between LCD and DLP is how they make up for the refractive qualities of light. Jump back to high school science, and recall how the different colours of light refract various amounts when shone through the same lens. The problem with DLP projectors is that they utilise the one same panel and the same lens to project Red, Blue and Green. All 3 colours are obviously different and refract light in different ways. Often with a DLP projector, a spill of yellow colour will be projected above and a superfluous blue will come through below an image containing something as simple as a lone black line. During manufacturing LCD projectors can be set to minimize these effects on the projected image, as each colour is projected on separate LCD panels.
The isolated true advantage (excluding price) with deciding on a DLP projector is its smaller overall size and weight. However, this is only relevant for mobility and needs to be traded off against the image plusses of LCD projectors. If resulting picture quality is vital to you, then the solution is easy. Go for an LCD projector! LCD projectors will definitely make bright, colourful images with fewer image errors. If you want to know more about LCD technology in more detail, have a gander at this spectacular resource website: Explore 3LCD. If you have any other questions, visit Projector Central and send me an email.
Jonathan King is the sales and marketing manager of Projector Central, Australia’s top online store for projectors. Brisbane based, Projector Central has been servicing Australia for 15 years. For data projectors in Brisbane and Interactive Whiteboards, contact Projector Central today.
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