Projectors: LCD Verses DLP (The downfall of DLP technology)
The most common question heard when buying a new projector for the home, office, or classroom is: do I take an LCD projector or a DLP projector? LCD, standing 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 models available, it can be difficult for customers to make a choice between these technologies. It comes down to the fact that LCD projectors provide far better image quality and colour accuracy. The next part of this article tells you why DLP projectors struggle with reproducing an equal grade of image quality.
Think of a set of blinds in your household on 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. Such is exactly how an LCD projector functions. Each pixel operates like an individual shutter on a set of blinds to either send light through or to block it. DLP on the other hand is constructed of millions of microscopic mirrors or ‘pixel elements’ as the pros like to call them. Each pixel element works to either reflect light or block it.
How the light source is processed from when the projector is turned on to when the content reaches your screen is absolutely important 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 direct the coloured light to 3 separate 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 send the projector image. An important point to understad about LCD projectors is that all three colours are projected onto your projector screen simultaneously. The way a DLP projector works is very different and even how an image looks is not the same. With DLP, white light from the lamp is processed through a rotating colour wheel with transparent red, blue and green segments, at speeds up to 11,000 rpm/s. This method of making an image creates a sequence of red, blue and green light. The millions of micro mirrors mentioned above reflect the coloured light on the pixels to create the image elements. The elements of the image are cast in sequence on the screen, one colour at a time. The viewer’s vision will then pull together each coloured element of the image into the single complete image. In LCD projectors, all colours are available all the time to deliver the highest brightness and spectacular colour accuracy. In DLP, just one colour is available at once, and so causing lower colour brightness and accuracy. Some manufacturers have put a white segment into the colour wheel to improve all over brightness, but this then lessens colour accuracy.
I hear in forums all the time that DLP provides a higher contrast ratio and as such 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 able to produce. DLP projectors do possess high contrast specifications in comparison to the majority of LCD projectors. At one glance, this must be a benefit, however, in truth, the true black level is determined by the ambient light in the room when the projector is being utilised. Do not be duped by contrast specifications on websites and in brochures.
When the content you wish to bring to life has moving images, DLP projection technology also has image errors, or ‘artifacts’. The most common 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 position between the time red, blue and green colours are pulled up. LCD projectors do not have this characteristic because all the colours are delivered with the others. DLP designers have come up with 3DLP solutions using 3 chips to fix the colour break up artifacts, but the expense of these projectors make them not 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. Remember back to high school science, and they taught you how different colours of light refract differing amounts when passing through the same lens. The problem with DLP projectors is that they use the one same panel and the same lens to project Red, Blue and Green. All 3 colours are different and refract light in a different way. Often with a DLP projector, some extra yellow colour will come up above and some extra blue will appear below something as simple as a straight black line. While being built LCD projectors can be set to reduce these effects on the projected image, as each colour is projected on a separate LCD panels.
The isolated true advantage (excluding price) with choosing a DLP projector is its smaller overall size and weight. However, this is only relevant to mobility and cannot be traded off against the image superiority of LCD projectors. If the result of the picture quality is vital to you, then the answer is easy. Go with an LCD projector! LCD projectors will consistently show bright, colourful images with fewer image errors. If you want to learn more about LCD technology in more detail, check out this tremendous resource website: Explore 3LCD. If you have any more 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 retailer for projectors. Brisbane based, Projector Central has been servicing Australia for 15 years. For data projectors in the Gold Coast and Interactive Whiteboards, contact Projector Central today.
