The most typical question heard when acquiring a new projector for the home, office, or classroom is: would I get an LCD projector or a DLP projector? LCD, short for ‘liquid crystal device’ and DLP, short for ‘digital light processing’ are the two most popular projector imaging technologies. With so many brands and different types available, it can be confusing for customers to make a choice between both technologies. Ultimately LCD projectors give better image quality and colour accuracy. The next part of this article will tell you why DLP projectors struggle with projecting a comparable standard of image quality.
Think of a set of blinds in your room covering your bedroom window. By pulling a rod you can turn the shutters open or closed, according to 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 allow light through or to block it. DLP on the other hand is constructed of millions of microscopic mirrors or ‘pixel elements’ as the pros like to call them. Each pixel element operates to either reflect light or block it.
How the light source is processed from the time the projector is switched on to when the picture reaches your screen is absolutely significant to image quality, brightness and colour accuracy. LCD projectors project white light from the lamp by splitting it into red, blue and green components, by three mirrors which send the coloured light to 3 separate LCD panels. The 3 LCD panels make the elements of the image by turning each pixel on and off. The pixels are then combined in a glass prism to create the projector image. Something important to understad about LCD projectors is that all three colours are delivered onto your projector screen all at once. The way a DLP projector functions is widely different and even the final product of how an image appears is not the same. With DLP, white light from the lamp is projected through a turning colour wheel with transparent red, blue and green segments, at speeds up to 11,000 rpm/s. This approach to making an image casts a sequence of red, blue and green light. The millions of micro mirrors as described above reflect the coloured light on the pixels to create 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 pull together each coloured element of the image into the single total image. Using LCD projectors, all colours are available all the time to deliver the highest brightness and spectacular colour accuracy. In DLP, just one colour is available at any given time, resulting in lower colour brightness and accuracy. Some DLP manufacturers have included a white segment for the colour wheel to improve all over brightness, but this further degrades colour accuracy.
I hear in forums all the time that DLP gives a higher contrast ratio and thus must be superior. 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 projector is capable of producing. DLP projectors do possess high contrast specifications when compared to many LCD projectors. At one glance, this appears to be an advantage, however, in real life, the true black level is determined by the ambient light in the room in which the projector is being used. Do not be hoodwinked by contrast specifications on websites and in brochures.
When the content you wish to bring to life has moving images, DLP projection technology also creates image imperfections, or ‘artifacts’. The most common artifact that a DLP projector displays with moving images is colour break up. Colour break up is incontrovertible in DLP systems because moving images change between the time red, blue and green colours are displayed. LCD projectors do not have this characteristic because all the colours are sent with the others. DLP manufacturers have created 3DLP solutions using 3 chips to answer the colour break up error, but the cost of these projectors make them impractical for the majority of businesses and consumers.
Another variance between LCD and DLP is how they compensate for the refractive qualities of light. Think back to high school science, and they taught you how the various colours of light refract differing 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 not the same and refract light in a different way. Most of the time with a DLP projector, a superfluous yellow colour will show above and some extra blue will show below something as simple as a single black line. In building LCD projectors can be adapted to reduce these effects on the projected image, as each colour is directed on isolated LCD panels.
The isolated veritable benefit (excluding price) with taking a DLP projector is its smaller overall size and weight. However, this is only relevant in regard to transporting the device and must be traded off against the image advantages of LCD projectors. If the outcome of the picture quality is important to you, then the solution is no-brainer. Choose an LCD projector! LCD projectors will always make bright, colourful images with fewer image imperfections. If you need to learn more about LCD technology in more detail, have a look at this fantastic resource website: Explore 3LCD. If you have any further questions, visit Projector Central and send me an email.
Jonathan King is the sales and marketing manager of Projector Central, Australia’s number one online store 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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