Mack and Mark

The common question customers ask when buying 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, standing for ‘digital light processing’ are the two commonplace projector imaging technologies. With so many different brands and different models available, it can be overwhelming for consumers to choose between the two technologies. Ultimately LCD projectors provide far superior image quality and colour accuracy. The next part of this article tells you why DLP projectors struggle with bringing up a similar level of image quality.

Imagine a set of blinds in your household over your bedroom window. By pulling a rod you can have 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 functions like its own shutter on a set of blinds to either shine light through or to block it. DLP on the other hand is made up 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 time the projector is switched on to when the image reaches your screen is ultimately important to image quality, brightness and colour accuracy. LCD projectors project white light from the lamp by dividing it into red, blue and green components, by three mirrors which transfer the coloured light to 3 individual LCD panels. The 3 LCD panels make the elements of the image by switching each pixel on and off. The pixels are then projected in a glass prism to create the projector image. Something to realise about LCD projectors is that all three colours are delivered onto your projected surface at once. The way a DLP projector operates is vastly different and even the way an image looks 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 forming an image casts 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 projected 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 single full image. Using LCD projectors, all colours are available all the time to create the best brightness and spectacular colour accuracy. In DLP, just one colour is available at once, and so causing lower colour brightness and accuracy. Some DLP developers have put a white segment in the colour wheel to improve brightness overall, but this then degrades colour accuracy.

I see in forums all the time that DLP provides a higher contrast ratio and therefore must be superior. For those unsure, 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 offer high contrast specifications as compared to a majority of LCD projectors. At one glance, this must be an advantage, however, in truth, the true black level is determined by the ambient light in the room when the projector is being used. Do not be tricked by contrast specifications on websites and in brochures.

When the content you wish to view includes moving images, DLP projection technology can also create image marks, or ‘artifacts’. The most commonplace artifact that a DLP projector creates with moving images is colour break up. Colour break up is inherent in DLP systems because moving images keep changing between the time red, blue and green colours are pulled up. LCD projectors do not have this downside because every colour is projected with the others. DLP manufacturers have created 3DLP solutions using 3 chips to fix the colour break up issue, but the price of these projectors make them almost impossible for many businesses and consumers.

Another point of difference between LCD and DLP is how they match the balance for the refractive qualities of light. Take yourself back to high school science, and recall when they taught you how the various colours of light refract various amounts when shone through the same lens. The downside with DLP projectors is that they take the one same panel and the same lens to project Red, Blue and Green. All 3 colours are obviously not the same and refract light differently. Usually with a DLP projector, some yellow colour will show above and a spill of blue will come up below an image containing something as simple as a lone black line. In building LCD projectors can be adapted to remove these effects on the projected image, because each colour is projected on separate LCD panels.

The isolated real plus (excluding price) with deciding on a DLP projector is its smaller total size and weight. However, this is only relevant in regard to transporting the device and has to be traded off against the image advantages of LCD projectors. If overall picture quality is vital to you, then the answer is simple. Choose an LCD projector! LCD projectors will always make bright, colourful images with fewer image blips. If you need to know more about LCD technology in more detail, check out this fabulous resource website: Explore 3LCD. If you have any further questions, go to Projector Central and send me an email.

Jonathan King is the sales and marketing manager of Projector Central, Australia’s top 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.