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

The common question that is asked when buying a new projector for the home, office, or classroom is: should I purchase 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 clients to pick between these technologies. Ultimately LCD projectors offer superior image quality and colour accuracy. The next paragraph will tell you why DLP projectors struggle with bringing up an equal grade of image quality.

Imagine a set of blinds in your room covering your bedroom window. By twisting a rod you can turn the shutters open or closed, depending on whether you want to let light in or not. And such is exactly how an LCD projector functions. Each pixel operates like a single shutter on a set of blinds to either allow light through or to block it. DLP on the other hand is constructed of millions of microscopic mirrors or ‘pixel elements’ as the experts like to call them. Each pixel element works to either reflect light or block it.

How the light source is processed from the point when the projector switches on to when the picture reaches your screen is vitally significant for 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 individual LCD panels. The 3 LCD panels form the elements of the image by turning each pixel on and off. The pixels are then meshed in a glass prism to deliver the projector image. A significant point to realise about LCD projectors is that all three colours are sent onto your screen all at once. The way a DLP projector works is totally different and even the way an image looks is not the same. With DLP, white light from the lamp is projected through a spinning colour wheel with transparent red, blue and green segments, at speeds up to 11,000 rpm/s. This way of projecting 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 form the image elements. The elements of the image are projected in sequence on the screen, one colour at a time. The viewer’s eyes will then put together each coloured element of the image into a single whole image. Using LCD projectors, all colours are available all the time to deliver high brightness and great colour accuracy. In DLP, just one colour is available at any given time, and so causing lower colour brightness and accuracy. Some DLP developers have included a white segment into the colour wheel to improve overall brightness, but this also lessens colour accuracy.

I read in forums all the time that DLP has 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 projector is able to produce. DLP projectors do provide high contrast specifications when compared to a majority of LCD projectors. At first glance, this seems to be a plus, however, in real life, the true black level is determined by the ambient light in the room while the projector is being used. Do not be fooled by contrast specifications on websites and in brochures.

When the content you wish to view requires moving images, DLP projection technology can also create image marks, or ‘artifacts’. The most often seen artifact that a DLP projector displays 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 projected. LCD projectors do not have this problem because all the colours are delivered at the same time. DLP manufacturers have come up with 3DLP solutions using 3 chips to answer the colour break up artifacts, but the expense of these projectors make them not practical for the large part of businesses and consumers.

Another point of difference between LCD and DLP is how they compensate for the refractive qualities of light. Remember back to high school science, and remember how different colours of light refract different amounts when directed through the same lens. The downside with DLP projectors is that they use the one same panel with the same lens to project Red, Blue and Green. All 3 colours are obviously different and refract light differently. Usually with a DLP projector, an extra yellow colour will come through above and a spill of blue will come up below an image of something as simple as a single black line. In manufacturing LCD projectors can be adjusted to remove these effects on the projected image, as each colour is processed on a separate LCD panels.

The sole real buy point (excluding price) with choosing a DLP projector is its smaller total size and weight. However, this is only relevant with regard to portability 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 choice is no-brainer. Go with an LCD projector! LCD projectors will constantly 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 spectacular resource website: Explore 3LCD. If you have any additional questions, jump onto Projector Central and send me an email.

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