Projectors: LCD Verses DLP (The downfall of DLP technology)
The most common question asked when looking for a new projector for the home, office, or classroom is: will I get an LCD projector or a DLP projector? LCD, which stands for ‘liquid crystal device’ and DLP, standing for ‘digital light processing’ are the two most common projector imaging technologies. With so many brands and models available, it can be confusing for the buyer to choose between these technologies. Ultimately LCD projectors have better image quality and colour accuracy. The next part of this article explains why DLP projectors struggle with bringing up a comparable standard of image quality.
Imagine a set of blinds in your house covering your bedroom window. By twisting a rod you can turn the shutters open or closed, depending on if you want to let light in or not. And this is exactly how an LCD projector works. Each pixel functions like its own 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 experts like to call them. Each pixel element works to either reflect light or block it.
How the light source is processed from when the projector switches on to when the image reaches your screen is absolutely significant in regard 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 transfer the coloured light to 3 separate LCD panels. The 3 LCD panels create the elements of the image by shining each pixel on and off. The pixels are then simultaneously processed in a glass prism to deliver the projector image. An important point to remember about LCD projectors is that all three colours are delivered onto your wall all at the same time. The way a DLP projector functions is vastly different and even the way an image appears is not the same. With DLP, white light from the lamp is directed through a rotating colour wheel with transparent red, blue and green segments, at speeds up to 11,000 rpm/s. This method of forming an image requires a sequence of red, blue and green light. The millions of micro mirrors as mentioned 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 eye will then draw each coloured element of the image into the single whole image. With LCD projectors, all colours are available all the time to form the highest brightness and spectacular colour accuracy. In DLP, just one colour is available at a time, resulting in lower colour brightness and accuracy. Some DLP developers have placed a white segment in the colour wheel to improve general brightness, but this then damages colour accuracy.
I find in forums all the time that DLP provides a higher contrast ratio and as such must be superior. For those uncertain, 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 capable of producing. DLP projectors do offer high contrast specifications as compared to a majority of LCD projectors. At a glance, this must be a benefit, however, in truth, the true black level is determined by the ambient light in the room in which the projector is used. Do not be tricked by contrast specifications on websites and in brochures.
When the content you wish to view has moving images, DLP projection technology can also have 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 incontrovertible in DLP systems because moving images change between the time red, blue and green colours are projected. LCD projectors do not have this disadvantage because the colours are projected simultaneously. DLP manufacturers have developed 3DLP solutions using 3 chips to resolve the colour break up artifacts, but the price of these projectors make them hardly practical for most businesses and consumers.
Another point of difference between LCD and DLP is how they match the balance for the refractive qualities of light. Take yourself back to high school science, and remember how the different colours of light refract various amounts when directed through the same lens. The problem 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 obviously not the same and refract light in a different way. Often with a DLP projector, some yellow colour will be projected above and a spill of blue will show below an image as simple as a straight black line. In manufacturing LCD projectors can be adjusted to take away these effects on the projected image, as each colour is directed on its own LCD panels.
The isolated actual plus (excluding price) with deciding on a DLP projector is its smaller overall size and weight. However, this is only relevant for mobility and must be traded off against the image benefits of LCD projectors. If resulting picture quality is crucial to you, then the solution is no-brainer. Go with an LCD projector! LCD projectors will always produce bright, colourful images with fewer image imperfections. If you need to ask more about LCD technology in more detail, see this fantastic resource website: Explore 3LCD. If you have any further questions, jump onto Projector Central and send me an email.
Jonathan King is the sales and marketing manager with Projector Central, Australia’s number one online shop 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.
