Projectors: LCD Verses DLP (The downfall of DLP technology)

July 19, 2010, 9:05 pm

The typical question heard when looking for a new projector for the home, office, or classroom is: would I get an LCD projector or a DLP projector? LCD, standing for ‘liquid crystal device’ and DLP, an acronym for ‘digital light processing’ are the two commonplace projector imaging technologies. With so many company brands and models available, it can be overwhelming for the buyer to make a decision between these technologies. The simple fact of the matter is that LCD projectors offer superior image quality and colour accuracy. The next part of this article will explain why DLP projectors struggle with bringing up a similar grade of image quality.

It’s like a set of blinds in your room for your bedroom window. By pulling on 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 behaves. Each pixel operates like a unique shutter on a set of blinds to either pass light through or to block it. DLP on the other hand is formed of millions of microscopic mirrors or ‘pixel elements’ as pros like to call them. Each pixel element operates to either reflect light or block it.

How the light source is processed from the point at which the projector is turned on to when the image reaches your screen is absolutely significant in regard to 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 project the coloured light to 3 stand alone LCD panels. The 3 LCD panels make the elements of the image by processing each pixel on and off. The pixels are then projected in a glass prism to send the projector image. A point to remember about LCD projectors is that all three colours are projected onto your projector screen all at once. 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 directed 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 described 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. In LCD projectors, all colours are available all the time to form the top level of brightness and fantastic colour accuracy. In DLP, only one colour is available at once, and so causing lower colour brightness and accuracy. Some DLP developers have included a white segment into the colour wheel to improve brightness overall, but this further detracts from colour accuracy.

I find in forums all the time that DLP provides a higher contrast ratio and therefore must be better. 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 provide high contrast specifications when compared to a majority of LCD projectors. At a glance, this seems to be a benefit, however, in truth, the true black level is determined by the ambient light in the room where the projector is used. Do not be tricked by contrast specifications on websites and in brochures.

When the content you plan to bring to life includes moving images, DLP projection technology also has image errors, or ‘artifacts’. The most commonplace artifact that a DLP projector displays with moving images is colour break up. Colour break up is unavoidable in DLP systems because moving images change position between the time red, blue and green colours are shone. LCD projectors do not have this downside because the colours are processed with the others. DLP designers have come up with 3DLP solutions using 3 chips to fix the colour break up issue, but the cost of these projectors make them impractical for the majority of businesses and consumers.

Another point of difference between LCD and DLP is how they match the balance for the refractive qualities of light. Jump back to high school science, and they taught you how different colours of light refract different amounts when passing through the same lens. The downside with DLP projectors is that they utilise the one same panel with the same lens to project Red, Blue and Green. All 3 colours are obviously different and refract light in different ways. Most of the time with a DLP projector, a spill of yellow colour will come up above and a superfluous blue will be projected below an image of something as simple as a straight black line. During manufacturing LCD projectors can be adapted to take away these effects on the projected image, as each colour is projected on separate LCD panels.

The sole true buy point (excluding price) with buying a DLP projector is its smaller overall size and weight. However, this is only relevant to portability and must be traded off against the image benefits of LCD projectors. If resulting picture quality is vital to you, then the choice is easy. Go with an LCD projector! LCD projectors will constantly show bright, colourful images with fewer image blips. If you need to learn more about LCD technology in more detail, have a look at this spectacular resource website: Explore 3LCD. If you have any persisting questions, go to Projector Central and send me an email.

Jonathan King is the sales and marketing manager with Projector Central, Australia’s premier online store for projectors. Brisbane based, Projector Central has been serving Australia for 15 years. For data projectors in Brisbane and Interactive Whiteboards, contact Projector Central today.