Projectors: LCD Verses DLP (The downfall of DLP technology)

The typical question asked when acquiring a new projector for the home, office, or classroom is: should I buy an LCD projector or a DLP projector? LCD, which stands for ‘liquid crystal device’ and DLP, standing for ‘digital light processing’ are the two commonplace projector imaging technologies. With so many brands and types available, it can be overwhelming for consumers to make a choice between these technologies. The fact is that LCD projectors offer superior image quality and colour accuracy. The article below will explain why DLP projectors struggle with bringing up the same grade of image quality.

Visualise a set of blinds in your room on your bedroom window. By pulling a rod you can have the shutters open or closed, depending on whether you want to let light in or not. That is exactly how an LCD projector behaves. Each pixel functions like its own shutter on a set of blinds to either allow light through or to block it. DLP on the other hand is made up 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 point when the projector turns on to when the picture reaches your screen is ultimately important with regard to image quality, brightness and colour accuracy. LCD projectors shine white light from the lamp by cutting it into red, blue and green components, by three mirrors which direct the coloured light to 3 different LCD panels. The 3 LCD panels form 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. An important point to understad about LCD projectors is that all three colours are projected onto your screen all at once. The way a DLP projector runs is widely different and even the final product of how an image comes out 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 method of projecting an image requires a sequence of red, blue and green light. The millions of micro mirrors mentioned above reflect the coloured light on the pixels to produce 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 a single total image. Using LCD projectors, all colours are available all the time to offer the top level of brightness and superb colour accuracy. In DLP, only one colour is available at any given time, resulting in lower colour brightness and accuracy. Some designers have included a white segment for the colour wheel to improve brightness generally, but this also damages colour accuracy.

I read in forums all the time that DLP gives a higher contrast ratio and therefore 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. DLP projectors do have high contrast specifications when compared to a majority of LCD projectors. At a glance, this must be a plus, 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 duped by contrast specifications on websites and in brochures.

When the content you want to see has moving images, DLP projection technology also creates image imperfections, or ‘artifacts’. The most often seen 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 up between the time red, blue and green colours are shone. LCD projectors do not have this characteristic because every colour is processed simultaneously. DLP designers have developed 3DLP solutions using 3 chips to solve the colour break up error, but the price tag of these projectors make them almost impossible for many businesses and consumers.

Another variance between LCD and DLP is how they make up for the refractive qualities of light. Think back to high school science, and they taught you how the different colours of light refract differing amounts when directed through the same lens. The downside with DLP projectors is that they have the one same panel with the same lens to project Red, Blue and Green. All 3 colours are obviously different and refract light differently. Usually with a DLP projector, some extra yellow colour will appear above and an extra blue will show below an image of something as simple as a straight black line. While being built LCD projectors can be set to take away these effects on the projected image, because each colour is projected on a separate LCD panels.

The sole actual advantage (excluding price) with choosing a DLP projector is its smaller overall size and weight. However, this is only relevant to transport and must be traded off against the image plusses of LCD projectors. If overall picture quality is crucial to you, then the decision is a no-brainer. Go with an LCD projector! LCD projectors will always make bright, colourful images with fewer image blips. If you want to know more about LCD technology in more detail, check out this spectacular resource website: Explore 3LCD. If you have any persisting questions, visit Projector Central and send me an email.

Jonathan King is the sales and marketing manager with Projector Central, Australia’s premier online provider for projectors. Brisbane based, Projector Central has serviced Australia for 15 years. For data projectors in Brisbane and Interactive Whiteboards, contact Projector Central today.