Projectors: LCD Verses DLP (The downfall of DLP technology)
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The most typical question heard when looking for a new projector for the home, office, or classroom is: will I buy an LCD projector or a DLP projector? LCD, an acronym for ‘liquid crystal device’ and DLP, standing for ‘digital light processing’ are the two most common projector imaging technologies. With so many business brands and different types available, it can be overwhelming for the buyer to make a choice between the two technologies. Ultimately LCD projectors give far superior image quality and colour accuracy. The next paragraph will tell you why DLP projectors struggle with bringing up a similar rate of image quality.
Visualise a set of blinds in your home 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 this is exactly how an LCD projector functions. Each pixel functions like a single shutter on a set of blinds to either pass light through or to block it. DLP on the other hand is created of millions of microscopic mirrors or ‘pixel elements’ as the experts 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 vitally significant with regard to image quality, brightness and colour accuracy. LCD projectors process white light from the lamp by dividing it into red, blue and green components, by three mirrors which project the coloured light to 3 different LCD panels. The 3 LCD panels make the elements of the image by shining each pixel on and off. The pixels are then combined in a glass prism to deliver the projector image. A significant point to know about LCD projectors is that all three colours are directed onto your screen simultaneously. The way a DLP projector runs is vastly different and even the produced image looks is not the same. With DLP, white light from the lamp is sent through a turning colour wheel with transparent red, blue and green segments, at speeds up to 11,000 rpm/s. This way of making an image forms a sequence of red, blue and green light. The millions of micro mirrors as described above reflect the coloured light on the pixels to produce 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 pull together each coloured element of the image into the single complete image. Using LCD projectors, all colours are available all the time to form high brightness and spectacular colour accuracy. In DLP, only one colour is available at any given time, resulting in lower colour brightness and accuracy. Some DLP designers have included a white segment into the colour wheel to improve brightness generally, but this then damages colour accuracy.
I see in forums all the time that DLP offers a higher contrast ratio and as such must be better. 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 provide high contrast specifications when compared to a majority of LCD projectors. At one glance, this seems to be a plus, however, in truth, 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 wish to project needs moving images, DLP projection technology also has image errors, or ‘artifacts’. The most often seen artifact that a DLP projector shows with moving images is colour break up. Colour break up is unavoidable 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 processed with the others. DLP developers have come up with 3DLP solutions using 3 chips to fix the colour break up issue, but the price tag of these projectors make them hardly practical for many businesses and consumers.
Another differentiation between LCD and DLP is how they compensate for the refractive qualities of light. Think back to high school science, and remember when they taught you how different colours of light refract different amounts when shone through the same lens. The downfall 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 not the same and refract light in different ways. Most of the time with a DLP projector, some extra yellow colour will appear above and a spill of blue will appear below an image of something as simple as a lone black line. In manufacturing LCD projectors can be set to reduce these effects on the projected image, as each colour is processed on separate LCD panels.
The isolated true buy point (excluding price) with picking a DLP projector is its smaller size and weight. However, this is only relevant in regard to mobility and cannot be traded off against the image benefits of LCD projectors. If overall picture quality is vital to you, then the solution is a no-brainer. Take an LCD projector! LCD projectors will always make bright, colourful images with fewer image errors. If you need to learn more about LCD technology in more detail, see this spectacular resource website: Explore 3LCD. If you have any more questions, jump onto Projector Central and send me an email.
Jonathan King is the sales and marketing manager for Projector Central, Australia’s top online retailer for projectors. Brisbane based, Projector Central has been servicing Australia for 15 years. For data projectors in Brisbane and Interactive Whiteboards, contact Projector Central today.
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