Projectors: LCD Verses DLP (The downfall of DLP technology)
The most typical question heard when buying a new projector for the home, office, or classroom is: should I take an LCD projector or a DLP projector? LCD, short for ‘liquid crystal device’ and DLP, which stands for ‘digital light processing’ are the two top projector imaging technologies. With so many company brands and different models available, it can be confusing for customers to decide between the two technologies. The fact is that LCD projectors offer far better image quality and colour accuracy. The next part of this article will explain why DLP projectors struggle with bringing up an equal standard of image quality.
Imagine a set of blinds in your room for your bedroom window. By a twist of a rod you can turn the shutters open or closed, depending on if you want to let light in or not. And that is exactly how an LCD projector behaves. Each pixel works like a unique 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 pros like to call them. Each pixel element operates 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 picture reaches your screen is absolutely important 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 send the coloured light to 3 stand alone 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 form the projector image. A significant point to remember about LCD projectors is that all three colours are sent onto your projector screen all at once. The way a DLP projector runs is vastly different and even the way an image shows up is not the same. With DLP, white light from the lamp is processed through a turning colour wheel with transparent red, blue and green segments, at speeds up to 11,000 rpm/s. This approach to creating an image requires a sequence of red, blue and green light. The millions of micro mirrors 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 eye will then put together each coloured element of the image into a complete image. In LCD projectors, all colours are available all the time to offer the highest brightness and superb colour accuracy. In DLP, only one colour is available at a time, resulting in lower colour brightness and accuracy. Some DLP manufacturers have placed a white segment in the colour wheel to improve brightness overall, but this goes and damages colour accuracy.
I hear in forums all the time that DLP has a higher contrast ratio and therefore must be better 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 system is able to produce. DLP projectors do offer high contrast specifications when compared to a majority of LCD projectors. At first glance, this must be an advantage, however, in real life, the true black level is determined by the ambient light in the room where the projector is being utilised. Do not be hoodwinked by contrast specifications on websites and in brochures.
When the content you are trying to view requires moving images, DLP projection technology also creates image imperfections, 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 change position between the time red, blue and green colours are displayed. LCD projectors do not have this problem because every colour is projected at the same time. DLP designers have formed 3DLP solutions using 3 chips to resolve the colour break up problem, but the price tag of these projectors make them hardly practical for many 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 recall when they taught you how the different colours of light refract varied amounts when directed through the same lens. The downside with DLP projectors is that they have the one same panel with the same lens to project Red, Blue and Green. All 3 colours are obviously different and refract light at different levels. Most of the time with a DLP projector, some yellow colour will come up above and a spill of blue will show below an image as simple as a lone black line. During manufacturing LCD projectors can be fixed to reduce these effects on the projected image, because each colour is refracted on separate LCD panels.
The one real buy point (excluding price) with picking a DLP projector is its smaller total size and weight. However, this is only relevant for mobility and has to be traded off against the image benefits of LCD projectors. If the outcome of the picture quality is important to you, then the solution is simple. Go with an LCD projector! LCD projectors will definitely produce bright, colourful images with fewer image errors. If you wish to ask more about LCD technology in more detail, see this spectacular resource website: Explore 3LCD. If you have any persisting questions, jump onto Projector Central and send me an email.
Jonathan King is the sales and marketing manager for Projector Central, Australia’s premier online store for projectors. Based in Brisbane, Projector Central has served Australia for 15 years. For data projectors in the Gold Coast and Interactive Whiteboards, contact Projector Central today.
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