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

The most typical question that is asked when acquiring a new projector for the home, office, or classroom is: should I purchase an LCD projector or a DLP projector? LCD, standing for ‘liquid crystal device’ and DLP, standing for ‘digital light processing’ are the two most common projector imaging technologies. With so many brands and different types available, it can be overwhelming for consumers to choose between both technologies. The simple fact of the matter is that LCD projectors have far better image quality and colour accuracy. The following article will explain why DLP projectors struggle with bringing up a similar level of image quality.

Visualise a set of blinds in your household covering your bedroom window. With the twist of a rod you can make the shutters open or closed, depending on whether you want to let light in or not. Such is exactly how an LCD projector behaves. Each pixel works like an individual 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 the experts like to call them. Each pixel element operates to either reflect light or block it.

How the light source is processed from the point at which the projector is turned on to when the content reaches your screen is ultimately significant with regard to image quality, brightness and colour accuracy. LCD projectors direct white light from the lamp by separating it into red, blue and green components, by three mirrors which project the coloured light to 3 different LCD panels. The 3 LCD panels cast the elements of the image by processing each pixel on and off. The pixels are then projected in a glass prism to create the projector image. Something to remember about LCD projectors is that all three colours are projected onto your projector screen at the same time. The way a DLP projector works is totally different and even the way an image shows up is not the same. With DLP, white light from the lamp is directed through a turning colour wheel with transparent red, blue and green segments, at speeds up to 11,000 rpm/s. This way of 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 produce 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 draw each coloured element of the image into a whole image. With 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 once, resulting in lower colour brightness and accuracy. Some DLP manufacturers have added a white segment for the colour wheel to improve overall brightness, but this also lessens colour accuracy.

I find in forums all the time that DLP has a higher contrast ratio and as such must be better 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 projector is capable of producing. DLP projectors do have high contrast specifications in comparison to many LCD projectors. Initially, this seems to be a benefit, however, in real life, the true black level is determined by the ambient light in the room when the projector is utilised. Do not be duped by contrast specifications on websites and in brochures.

When the content you are trying to view requires moving images, DLP projection technology can also create image imperfections, or ‘artifacts’. The most common artifact that a DLP projector shows with moving images is colour break up. Colour break up is inherent in DLP systems because moving images change position between the time red, blue and green colours are displayed. LCD projectors do not have this disadvantage because all the colours are delivered simultaneously. DLP designers have created 3DLP solutions using 3 chips to fix the colour break up issue, but the cost of these projectors make them hardly practical for the majority of businesses and consumers.

Another variance between LCD and DLP is how they balance for the refractive qualities of light. Remember back to high school science, and they taught you how the various colours of light refract various amounts when passing through the same lens. The problem with DLP projectors is that they take the one same panel with the same lens to project Red, Blue and Green. All 3 colours are different and refract light differently. Often with a DLP projector, some yellow colour will come up above and an extra blue will be projected below an image containing something as simple as a straight black line. During manufacturing LCD projectors can be fixed to reduce these effects on the projected image, because each colour is refracted on separate LCD panels.

The isolated veritable advantage (excluding price) with taking 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 plusses of LCD projectors. If resulting picture quality is crucial to you, then the choice is a no-brainer. Go for an LCD projector! LCD projectors will consistently make bright, colourful images with fewer image errors. If you need to find out more about LCD technology in more detail, check out 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 with Projector Central, Australia’s premier online retailer for projectors. Brisbane-based, Projector Central has serviced Australia for 15 years. For data projectors in Brisbane and Interactive Whiteboards, contact Projector Central today.