The typical question heard when purchasing a new projector for the home, office, or classroom is: should I take an LCD projector or a DLP projector? LCD, an acronym for ‘liquid crystal device’ and DLP, an acronym for ‘digital light processing’ are the two most popular projector imaging technologies. With so many different brands and different types available, it can be overwhelming for the buyer to decide between both technologies. The simple fact of the matter is that LCD projectors offer far better image quality and colour accuracy. The following article will explain why DLP projectors struggle with bringing up a comparable rate of image quality.
Visualise a set of blinds in your room on your bedroom window. With the twist of a rod you can turn the shutters open or closed, according to if you want to let light in or not. That is exactly how an LCD projector behaves. Each pixel functions like an individual shutter on a set of blinds to either pass 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 time the projector is turned on to when the content reaches your screen is absolutely significant with regard to image quality, brightness and colour accuracy. LCD projectors direct white light from the lamp by separating it into red, blue and green components, by three mirrors which direct the coloured light to 3 different LCD panels. The 3 LCD panels create the elements of the image by processing each pixel on and off. The pixels are then simultaneously processed in a glass prism to form the projector image. Something to understad about LCD projectors is that all three colours are directed onto your wall at the same time. The way a DLP projector works is widely different and even how an image shows up is not the same. With DLP, white light from the lamp is directed 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 forms 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 sent in sequence on the screen, one colour at a time. The viewer’s vision will then put together each coloured element of the image into the complete image. From LCD projectors, all colours are available all the time to offer the top level of brightness and great colour accuracy. In DLP, just one colour is available at a time, resulting in lower colour brightness and accuracy. Some DLP designers have put a white segment in the colour wheel to improve all over brightness, but this further degrades colour accuracy.
I hear in forums all the time that DLP offers a higher contrast ratio and ergo must be superior. For those who don’t know, 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 technology is able to produce. DLP projectors do provide high contrast specifications as compared to the majority of LCD projectors. At first glance, this must be an advantage, however, in truth, the true black level is determined by the ambient light in the room in which the projector is in use. Do not be fooled by contrast specifications on websites and in brochures.
When the content you wish to view has moving images, DLP projection technology also creates 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 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 problem because all colours are delivered simultaneously. DLP designers have come up with 3DLP solutions using 3 chips to resolve the colour break up error, but the price tag of these projectors make them not practical for most 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 various amounts when shone through the same lens. The disadvantage with DLP projectors is that they have the one same panel and the same lens to project Red, Blue and Green. All 3 colours are not the same and refract light in different ways. Usually with a DLP projector, some extra yellow colour will come up above and some blue will appear below an image of something as simple as a single black line. While being built LCD projectors can be adapted to minimize these effects on the projected image, because each colour is projected on its own LCD panels.
The sole real advantage (excluding price) with picking a DLP projector is its overall smaller size and weight. However, this is only relevant to transport and must be traded off against the image benefits of LCD projectors. If overall picture quality is vital to you, then the solution is no-brainer. Choose an LCD projector! LCD projectors will constantly make bright, colourful images with fewer image errors. If you need to learn more about LCD technology in more detail, have a look at this tremendous resource website: Explore 3LCD. If you have any other questions, visit Projector Central and send me an email.
Jonathan King is the sales and marketing manager of Projector Central, Australia’s premier 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.
