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

July 19th, 2010

The most common question heard when purchasing a new projector for the home, office, or classroom is: do I buy an LCD projector or a DLP projector? LCD, short for ‘liquid crystal device’ and DLP, standing for ‘digital light processing’ are the two commonplace projector imaging technologies. With so many company brands and models available, it can be challenging for consumers to make a choice between those technologies. It comes down to the fact that LCD projectors give far better image quality and colour accuracy. The next part of this article will tell you why DLP projectors struggle with creating a comparable rate of image quality.

It’s like a set of blinds in your home covering your bedroom window. By twisting a rod you can make the shutters open or closed, depending on if you want to let light in or not. Such is exactly how an LCD projector behaves. Each pixel works 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 professionals like to call them. Each pixel element functions to either reflect light or block it.

How the light source is processed from the point at which the projector is switched on to when the content reaches your screen is ultimately significant for 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 transfer the coloured light to 3 separate LCD panels. The 3 LCD panels cast the elements of the image by switching each pixel on and off. The pixels are then meshed in a glass prism to form the projector image. An important point to understad about LCD projectors is that all three colours are directed onto your wall simultaneously. The way a DLP projector operates is widely different and even how an image shows up is not the same. With DLP, white light from the lamp is sent through a spinning colour wheel with transparent red, blue and green segments, at speeds up to 11,000 rpm/s. This way of forming an image creates a sequence of red, blue and green light. The millions of micro mirrors described above reflect the coloured light on the pixels to create the image elements. The elements of the image are displayed in sequence on the screen, one colour at a time. The viewer’s eyes will then draw each coloured element of the image into a single total image. Using LCD projectors, all colours are available all the time to offer the highest brightness and spectacular colour accuracy. In DLP, only one colour is available at once, and so resulting in lower colour brightness and accuracy. Some manufacturers have included a white segment in 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 better. For those who are 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 able to produce. DLP projectors do provide high contrast specifications when compared to a majority of LCD projectors. At a glance, this can seem to be a plus, however, in reality, the true black level is determined by the ambient light in the room when the projector is being utilised. Do not be fooled by contrast specifications on websites and in brochures.

When the content you are trying to bring to life needs moving images, DLP projection technology can also have image errors, or ‘artifacts’. The most typical artifact that a DLP projector forms with moving images is colour break up. Colour break up is to be expected in DLP systems because moving images change up between the time red, blue and green colours are projected. LCD projectors do not have this characteristic because every colour is sent at the same time. DLP builders have developed 3DLP solutions using 3 chips to resolve the colour break up issue, but the price of these projectors make them hardly practical for many businesses and consumers.

Another differentiation between LCD and DLP is how they balance for the refractive qualities of light. Remember back to high school science, and recall how the different colours of light refract various amounts when directed through the same lens. The downside 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 obviously different and refract light in different ways. Often with a DLP projector, some yellow colour will come through above and some blue will appear below an image of something as simple as a lone black line. While being built LCD projectors can be adjusted to minimize these effects on the projected image, as each colour is refracted on isolated LCD panels.

The one real plus (excluding price) with choosing a DLP projector is its smaller size and weight. However, this is only relevant for transport and cannot be traded off against the image advantages of LCD projectors. If resulting picture quality is crucial to you, then the choice is simple. Go for an LCD projector! LCD projectors will always produce bright, colourful images with fewer image imperfections. If you want to learn more about LCD technology in more detail, have a gander at this fantastic 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 at Projector Central, Australia’s premier online shop for projectors. Based in Brisbane, Projector Central has been serving Australia for 15 years. For data projectors in the Gold Coast and Interactive Whiteboards, contact Projector Central today.

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