Projectors: LCD Verses DLP (The downfall of DLP technology)
The most typical question customers ask when purchasing a new projector for the home, office, or classroom is: do I buy an LCD projector or a DLP projector? LCD, which stands for ‘liquid crystal device’ and DLP, which stands for ‘digital light processing’ are the two commonplace projector imaging technologies. With so many different brands and types available, it can be difficult for the buyer to make a decision between those technologies. The fact is that LCD projectors have far superior image quality and colour accuracy. The article below tells you why DLP projectors struggle with reproducing a comparable standard of image quality.
Imagine a set of blinds in your room 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 functions. Each pixel functions like its own shutter on a set of blinds to either allow light through or to block it. DLP on the other hand is created of millions of microscopic mirrors or ‘pixel elements’ as professionals 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 turns on to when the content reaches your screen is vitally important with regard to image quality, brightness and colour accuracy. LCD projectors direct white light from the lamp by cutting it into red, blue and green components, by three mirrors which direct the coloured light to 3 individual LCD panels. The 3 LCD panels form the elements of the image by shining each pixel on and off. The pixels are then combined in a glass prism to form the projector image. Something to understad about LCD projectors is that all three colours are sent onto your projected surface at the same time. The way a DLP projector works is very different and even the produced image looks is not the same. With DLP, white light from the lamp is projected through a turning colour wheel with transparent red, blue and green segments, at speeds up to 11,000 rpm/s. This way of projecting 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 produce the image elements. The elements of the image are cast 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 offer top brightness and fantastic colour accuracy. In DLP, just one colour is available at any given time, causing lower colour brightness and accuracy. Some manufacturers have placed a white segment in the colour wheel to improve overall brightness, but this further damages colour accuracy.
I read in forums all the time that DLP gives a higher contrast ratio and ergo must be better. For those who do not know, 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 projector is capable of. DLP projectors do possess high contrast specifications when compared to most LCD projectors. At one glance, this must be a benefit, however, in the real world, the true black level is determined by the ambient light in the room where the projector is utilised. Do not be tricked by contrast specifications on websites and in brochures.
When the content you want to project requires moving images, DLP projection technology can also have image imperfections, or ‘artifacts’. The most commonplace 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 up between the time red, blue and green colours are projected. LCD projectors do not have this downside because every colour is projected simultaneously. DLP builders have formed 3DLP solutions using 3 chips to answer the colour break up artifacts, but the price tag of these projectors make them hardly practical for the majority of businesses and consumers.
Another variance between LCD and DLP is how they compensate for the refractive qualities of light. Remember back to high school science, and remember how the different colours of light refract varied amounts when directed through the same lens. The downfall with DLP projectors is that they utilise the one same panel for the same lens to project Red, Blue and Green. All 3 colours are different and refract light in different ways. Often with a DLP projector, an extra yellow colour will come up above and a spill of blue will appear below an image of something as simple as a lone black line. In manufacturing LCD projectors can be fixed to remove these effects on the projected image, because each colour is directed on separate LCD panels.
The only veritable advantage (excluding price) with taking a DLP projector is its smaller overall size and weight. However, this is only relevant with regard to portability and has to be traded off against the image benefits of LCD projectors. If the result of the picture quality is important to you, then the answer is a no-brainer. Take an LCD projector! LCD projectors will constantly produce bright, colourful images with fewer image imperfections. If you wish to know more about LCD technology in more detail, see this tremendous resource website: Explore 3LCD. If you have any other questions, jump onto Projector Central and send me an email.
Jonathan King is the sales and marketing manager with Projector Central, Australia’s top online store for projectors. Based in Brisbane, 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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