Projectors: LCD Verses DLP (The downfall of DLP technology)
The most common question heard when purchasing a new projector for the home, office, or classroom is: will I buy an LCD projector or a DLP projector? LCD, which stands for ‘liquid crystal device’ and DLP, an acronym for ‘digital light processing’ are the two commonplace projector imaging technologies. With so many business brands and different models available, it can be difficult for clients to pick between these technologies. The fact is that LCD projectors offer far superior image quality and colour accuracy. The next part of this article will tell you why DLP projectors struggle with reproducing a similar level of image quality.
Imagine a set of blinds in your household over your bedroom window. By a twist of a rod you can turn the shutters open or closed, according to if you want to let light in or not. And that is exactly how an LCD projector behaves. Each pixel functions like its own 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 professionals like to call them. Each pixel element operates to either reflect light or block it.
How the light source is processed from the point when the projector is turned on to when the content reaches your screen is absolutely important with regard to image quality, brightness and colour accuracy. LCD projectors direct white light from the lamp by dividing it into red, blue and green components, by three mirrors which send the coloured light to 3 separate LCD panels. The 3 LCD panels create the elements of the image by switching each pixel on and off. The pixels are then projected in a glass prism to deliver the projector image. Something to realise about LCD projectors is that all three colours are sent onto your projector screen at the same time. The way a DLP projector runs is totally different and even the final product of how an image shows up is not the same. With DLP, white light from the lamp is sent through a rotating colour wheel with transparent red, blue and green segments, at speeds up to 11,000 rpm/s. This approach to forming an image requires a sequence of red, blue and green light. The millions of micro mirrors described above reflect the coloured light on the pixels to construct the image elements. The elements of the image are displayed 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 complete image. From LCD projectors, all colours are available all the time to create high brightness and superb colour accuracy. In DLP, just one colour is available at any given time, causing lower colour brightness and accuracy. Some manufacturers have put 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 offers a higher contrast ratio and thus must be better quality. For those unsure, 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 able to produce. DLP projectors do have high contrast specifications compared to a majority of LCD projectors. At first glance, this can seem to be a benefit, however, in real life, the true black level is determined by the ambient light in the room while the projector is being used. Do not be duped by contrast specifications on websites and in brochures.
When the content you wish to see requires moving images, DLP projection technology also creates image errors, or ‘artifacts’. The most commonplace artifact that a DLP projector creates 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 shone. LCD projectors do not have this downside because every colour is projected simultaneously. DLP developers have formed 3DLP solutions using 3 chips to fix the colour break up error, but the cost of these projectors make them hardly practical for the large part of businesses and consumers.
Another difference between LCD and DLP is how they make up for the refractive qualities of light. Jump back to high school science, and they taught you how various colours of light refract various amounts when shone through the same lens. The problem with DLP projectors is that they use the one same panel for the same lens to project Red, Blue and Green. All 3 colours are different and refract light in a different way. Often with a DLP projector, a superfluous yellow colour will come up above and some extra blue will be projected below an image containing something as simple as a straight black line. In manufacturing LCD projectors can be adjusted to remove these effects on the projected image, because each colour is refracted on isolated LCD panels.
The one veritable advantage (excluding price) with taking a DLP projector is its overall smaller size and weight. However, this is only relevant to transport and has to be traded off against the image plusses of LCD projectors. If the outcome of the picture quality is vital to you, then the decision is no-brainer. Go for an LCD projector! LCD projectors will always make bright, colourful images with fewer image imperfections. If you want to learn more about LCD technology in more detail, have a gander at this fabulous 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 with Projector Central, Australia’s premier online retailer for projectors. Brisbane based, Projector Central has been serving Australia for 15 years. For data projectors in the Gold Coast and Interactive Whiteboards, contact Projector Central today.