The most common question customers ask when acquiring a new projector for the home, office, or classroom is: do I buy an LCD projector or a DLP projector? LCD, an acronym for ‘liquid crystal device’ and DLP, which stands for ‘digital light processing’ are the two most common projector imaging technologies. With so many brands and different types available, it can be difficult for consumers to make a decision between the two technologies. The fact is that LCD projectors provide far superior image quality and colour accuracy. The next paragraph explains why DLP projectors struggle with projecting a similar level of image quality.
Think of a set of blinds in your home for your bedroom window. By pulling on a rod you can make the shutters open or closed, depending on if you want to let light in or not. And that is exactly how an LCD projector operates. Each pixel operates like its own shutter on a set of blinds to either shine light through or to block it. DLP on the other hand is created of millions of microscopic mirrors or ‘pixel elements’ as pros like to call them. Each pixel element functions to either reflect light or block it.
How the light source is processed from when the projector turns on to when the image reaches your screen is vitally important to image quality, brightness and colour accuracy. LCD projectors process white light from the lamp by splitting it into red, blue and green components, by three mirrors which direct the coloured light to 3 different LCD panels. The 3 LCD panels cast the elements of the image by shining each pixel on and off. The pixels are then projected in a glass prism to deliver the projector image. An important point to remember about LCD projectors is that all three colours are projected onto your projector screen all at the same time. The way a DLP projector works is totally different and even how an image looks 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 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 cast in sequence on the screen, one colour at a time. The viewer’s vision will then pull together each coloured element of the image into the single complete image. From LCD projectors, all colours are available all the time to create top brightness and spectacular colour accuracy. In DLP, just one colour is available at a time, and so causing lower colour brightness and accuracy. Some designers have placed a white segment into the colour wheel to improve brightness overall, but this then lessens colour accuracy.
I find in forums all the time that DLP gives a higher contrast ratio and therefore must be superior 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 technology is capable of. DLP projectors do offer high contrast specifications when compared to the majority of LCD projectors. At one glance, this appears to be an advantage, however, in reality, the true black level is determined by the ambient light in the room when the projector is in use. Do not be tricked by contrast specifications on websites and in brochures.
When the content you plan to see includes 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 keep changing between the time red, blue and green colours are shone. LCD projectors do not have this disadvantage because all colours are delivered at once. DLP builders have formed 3DLP solutions using 3 chips to answer the colour break up artifacts, but the expense of these projectors make them not practical for many businesses and consumers.
Another differentiation between LCD and DLP is how they compensate for the refractive qualities of light. Jump back to high school science, and they taught you how the various colours of light refract different amounts when shone through the same lens. The disadvantage 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 not the same and refract light at different levels. Usually with a DLP projector, some extra yellow colour will come up above and some extra blue will come through below an image containing something as simple as a single black line. In manufacturing LCD projectors can be adapted to reduce these effects on the projected image, because each colour is projected on separate LCD panels.
The sole true benefit (excluding price) with deciding on a DLP projector is its smaller total size and weight. However, this is only relevant in regard to mobility and must be traded off against the image superiority of LCD projectors. If resulting picture quality is important to you, then the decision is a no-brainer. Choose an LCD projector! LCD projectors will definitely create bright, colourful images with fewer image errors. If you want to find out more about LCD technology in more detail, see this fabulous resource website: Explore 3LCD. If you have any other questions, jump onto Projector Central and send me an email.
Jonathan King is the sales and marketing manager for Projector Central, Australia’s leading online provider for projectors. Based in Brisbane, Projector Central has served Australia for 15 years. For data projectors in Brisbane and Interactive Whiteboards, contact Projector Central today.