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

The most common question that is asked when acquiring a new projector for the home, office, or classroom is: should I get 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 top projector imaging technologies. With so many company brands and different models available, it can be confusing for consumers to decide between those technologies. Ultimately LCD projectors offer far superior image quality and colour accuracy. The article below will explain why DLP projectors struggle with projecting an equal grade of image quality.

Imagine a set of blinds in your house covering your bedroom window. By twisting a rod you can have the shutters open or closed, according to if you want to let light in or not. This is exactly how an LCD projector functions. Each pixel functions like its own shutter on a set of blinds to either shine light through or to block it. DLP on the other hand is formed of millions of microscopic mirrors or ‘pixel elements’ as the pros like to call them. Each pixel element works to either reflect light or block it.

How the light source is processed from the point at which the projector turns on to when the picture reaches your screen is ultimately significant to image quality, brightness and colour accuracy. LCD projectors process white light from the lamp by separating it into red, blue and green components, by three mirrors which send the coloured light to 3 individual LCD panels. The 3 LCD panels create the elements of the image by turning each pixel on and off. The pixels are then projected in a glass prism to deliver the projector image. An important point to understad about LCD projectors is that all three colours are projected onto your screen at once. The way a DLP projector operates is totally different and even the produced image appears is not the same. With DLP, white light from the lamp is processed through a rotating colour wheel with transparent red, blue and green segments, at speeds up to 11,000 rpm/s. This method of projecting an image casts a sequence of red, blue and green light. The millions of micro mirrors mentioned above reflect the coloured light on the pixels to construct the image elements. The elements of the image are projected 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 a single total image. From LCD projectors, all colours are available all the time to deliver the top level of brightness and great colour accuracy. In DLP, only one colour is available at any given time, resulting in lower colour brightness and accuracy. Some DLP manufacturers have added a white segment in the colour wheel to improve brightness generally, but this then detracts from colour accuracy.

I read in forums all the time that DLP gives a higher contrast ratio and ergo must be superior. For those who are 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 capable of producing. DLP projectors do possess high contrast specifications as compared to the majority of LCD projectors. Initially, this appears to be a benefit, however, in reality, the true black level is determined by the ambient light in the room while the projector is used. Do not be duped by contrast specifications on websites and in brochures.

When the content you wish to bring to life includes moving images, DLP projection technology also has image errors, or ‘artifacts’. The most typical artifact that a DLP projector shows with moving images is colour break up. Colour break up is incontrovertible in DLP systems because moving images change position between the time red, blue and green colours are pulled up. LCD projectors do not have this downside because all colours are sent at once. DLP builders have developed 3DLP solutions using 3 chips to resolve the colour break up error, but the cost of these projectors make them not practical for most businesses and consumers.

Another point of difference between LCD and DLP is how they compensate for the refractive qualities of light. Jump back to high school science, and recall how the different colours of light refract different amounts when passing through the same lens. The downfall with DLP projectors is that they utilise 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, a superfluous yellow colour will appear above and an extra blue will appear below an image containing something as simple as a lone black line. In building LCD projectors can be set to take away these effects on the projected image, as each colour is projected on its own LCD panels.

The only true buy point (excluding price) with picking a DLP projector is its overall smaller size and weight. However, this is only relevant in regard to transport and must be traded off against the image advantages of LCD projectors. If resulting picture quality is crucial to you, then the answer is simple. Choose an LCD projector! LCD projectors will consistently create bright, colourful images with fewer image mistakes. If you want to ask more about LCD technology in more detail, have a look at this fabulous 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 for Projector Central, Australia’s leading online shop for projectors. Brisbane based, Projector Central has served Australia for 15 years. For data projectors in Brisbane and Interactive Whiteboards, contact Projector Central today.