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

The common question asked when looking for a new projector for the home, office, or classroom is: should I get 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 different brands and different models available, it can be confusing for customers to choose between these technologies. The simple fact of the matter is that LCD projectors have better image quality and colour accuracy. The next paragraph will explain why DLP projectors struggle with projecting the same rate of image quality.

Imagine a set of blinds in your room covering your bedroom window. By a twist of a rod you can have the shutters open or closed, according to if you want to let light in or not. Such is exactly how an LCD projector behaves. Each pixel functions like its own shutter on a set of blinds to either pass 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 operates to either reflect light or block it.

How the light source is processed from when the projector switches on to when the image reaches your screen is extremely important to image quality, brightness and colour accuracy. LCD projectors direct white light from the lamp by splitting it into red, blue and green components, by three mirrors which send the coloured light to 3 individual LCD panels. The 3 LCD panels make the elements of the image by shining each pixel on and off. The pixels are then simultaneously processed in a glass prism to deliver the projector image. Something important to realise about LCD projectors is that all three colours are sent onto your screen at once. The way a DLP projector functions is very different and even the produced image shows up 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 method of forming 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 construct 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 combine each coloured element of the image into a single complete image. In LCD projectors, all colours are available all the time to create the best brightness and superb colour accuracy. In DLP, just one colour is available at once, and so resulting in lower colour brightness and accuracy. Some DLP manufacturers have included a white segment for the colour wheel to improve overall brightness, but this further detracts from 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 system is capable of producing. DLP projectors do provide high contrast specifications as compared to a majority of LCD projectors. At a glance, this seems to be a plus, however, in truth, the true black level is determined by the ambient light in the room in which the projector is used. Do not be tricked by contrast specifications on websites and in brochures.

When the content you wish to bring to life has moving images, DLP projection technology also creates image errors, or ‘artifacts’. The most common artifact that a DLP projector forms 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 displayed. LCD projectors do not have this problem because all the colours are sent at the same time. DLP builders have developed 3DLP solutions using 3 chips to solve the colour break up problem, but the price of these projectors make them not practical 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. Remember back to high school science, and recall when they taught you how different colours of light refract differing amounts when shone through the same lens. The downfall 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 different and refract light in a different way. Most of the time with a DLP projector, a spill of yellow colour will be projected above and some blue will show below an image of something as simple as a lone black line. In building LCD projectors can be adjusted to remove these effects on the projected image, because each colour is projected on separate LCD panels.

The isolated true plus (excluding price) with choosing a DLP projector is its overall smaller size and weight. However, this is only relevant with regard to transport and has to be traded off against the image plusses of LCD projectors. If overall picture quality is important to you, then the choice is a no-brainer. Go with an LCD projector! LCD projectors will constantly show bright, colourful images with fewer image mistakes. If you want to know more about LCD technology in more detail, have a look at this spectacular resource website: Explore 3LCD. If you have any further questions, jump onto Projector Central and send me an email.

Jonathan King is the sales and marketing manager of Projector Central, Australia’s premier online shop for projectors. Brisbane based, Projector Central has serviced Australia for 15 years. For data projectors in the Gold Coast and Interactive Whiteboards, contact Projector Central today.

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