Projectors: LCD Verses DLP (The downfall of DLP technology)
The most typical question customers ask when acquiring a new projector for the home, office, or classroom is: would 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 brands and different types available, it can be confusing for the buyer to pick between the two technologies. The fact is that LCD projectors offer far superior image quality and colour accuracy. The next paragraph will explain why DLP projectors struggle with reproducing the same grade of image quality.
Imagine a set of blinds in your house over your bedroom window. By pulling on a rod you can turn the shutters open or closed, according to if you want to let light in or not. And that is exactly how an LCD projector behaves. Each pixel functions like a single 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 functions to either reflect light or block it.
How the light source is processed from the point at which the projector switches on to when the image reaches your screen is ultimately important with regard to image quality, brightness and colour accuracy. LCD projectors project white light from the lamp by cutting it into red, blue and green components, by three mirrors which direct the coloured light to 3 stand alone LCD panels. The 3 LCD panels make the elements of the image by turning each pixel on and off. The pixels are then simultaneously processed in a glass prism to form the projector image. Something important to remember about LCD projectors is that all three colours are projected onto your wall at once. The way a DLP projector operates is totally different and even the way an image looks is not the same. With DLP, white light from the lamp is sent 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 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 sent in sequence on the screen, one colour at a time. The viewer’s eye will then put together each coloured element of the image into the total image. With LCD projectors, all colours are available all the time to create the top level of brightness and great colour accuracy. In DLP, just one colour is available at a time, causing lower colour brightness and accuracy. Some DLP designers have placed a white segment in the colour wheel to improve brightness generally, but this goes and degrades colour accuracy.
I read in forums all the time that DLP offers a higher contrast ratio and therefore 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 technology is capable of. DLP projectors do provide high contrast specifications when compared to the majority of LCD projectors. At a glance, this can seem to be a benefit, however, in truth, the true black level is determined by the ambient light in the room while the projector is being used. Do not be duped by contrast specifications on websites and in brochures.
When the content you plan to project requires moving images, DLP projection technology also creates image imperfections, or ‘artifacts’. The most common 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 downside because every colour is delivered at once. DLP manufacturers have come up with 3DLP solutions using 3 chips to fix the colour break up error, but the cost of these projectors make them impractical for many businesses and consumers.
Another differentiation between LCD and DLP is how they balance for the refractive qualities of light. Think back to high school science, and recall when they taught you how different colours of light refract different amounts when directed through the same lens. The downside with DLP projectors is that they take the one same panel for the same lens to project Red, Blue and Green. All 3 colours are obviously different and refract light in a different way. Generally with a DLP projector, an extra yellow colour will show above and an extra blue will show below an image as simple as a single black line. In building LCD projectors can be set to minimize these effects on the projected image, because each colour is directed on its own LCD panels.
The one actual buy point (excluding price) with buying a DLP projector is its smaller 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 overall picture quality is crucial to you, then the decision is easy. Go with an LCD projector! LCD projectors will always produce bright, colourful images with fewer image blips. If you need to find out more about LCD technology in more detail, have a look at this tremendous resource website: Explore 3LCD. If you have any more questions, visit Projector Central and send me an email.
Jonathan King is the sales and marketing manager of Projector Central, Australia’s top online shop for projectors. Based in Brisbane, 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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