Roger Out

The common question customers ask when acquiring a new projector for the home, office, or classroom is: will I get an LCD projector or a DLP projector? LCD, an acronym for ‘liquid crystal device’ and DLP, which stands for ‘digital light processing’ are the two most common projector imaging technologies. With so many company brands and different models available, it can be confusing for the buyer to pick between those technologies. It comes down to the fact that LCD projectors give better image quality and colour accuracy. The next part of this article will explain why DLP projectors struggle with projecting the same level of image quality.

It’s like a set of blinds in your household on 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. And that is exactly how an LCD projector works. Each pixel works like its own shutter on a set of blinds to either pass light through or to block it. DLP on the other hand is constructed 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 is turned on to when the picture reaches your screen is extremely important in 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 individual LCD panels. The 3 LCD panels make the elements of the image by processing each pixel on and off. The pixels are then meshed in a glass prism to create the projector image. Something important to understad about LCD projectors is that all three colours are sent onto your projector screen all at once. The way a DLP projector runs is vastly different and even the produced image shows up 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 forming an image creates a sequence of red, blue and green light. The millions of micro mirrors as 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 eyes will then pull together each coloured element of the image into a single complete image. In LCD projectors, all colours are available all the time to offer high brightness and spectacular colour accuracy. In DLP, only one colour is available at once, and so resulting in lower colour brightness and accuracy. Some DLP manufacturers have placed a white segment for the colour wheel to improve brightness generally, but this also degrades colour accuracy.

I hear in forums all the time that DLP offers a higher contrast ratio and as such must be better quality. For those who don’t know, 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 have high contrast specifications when compared to a majority of LCD projectors. At a glance, this seems to be an advantage, however, in the real world, the true black level is determined by the ambient light in the room when the projector is in use. Do not be tricked by contrast specifications on websites and in brochures.

When the content you want to see has moving images, DLP projection technology can also create image imperfections, or ‘artifacts’. The most typical artifact that a DLP projector forms 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 pulled up. LCD projectors do not have this problem because all colours are sent simultaneously. DLP developers have developed 3DLP solutions using 3 chips to solve the colour break up error, but the expense of these projectors make them hardly practical for the large part of businesses and consumers.

Another difference between LCD and DLP is how they compensate for the refractive qualities of light. Think back to high school science, and recall when they taught you how the various colours of light refract varied amounts when directed through the same lens. The downfall with DLP projectors is that they take the one same panel and the same lens to project Red, Blue and Green. All 3 colours are not the same and refract light differently. Most of the time with a DLP projector, some extra yellow colour will come through above and some extra blue will show below an image as simple as a single black line. During 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 true advantage (excluding price) with choosing a DLP projector is its smaller overall size and weight. However, this is only relevant to portability and must be traded off against the image advantages of LCD projectors. If the outcome of the picture quality is vital to you, then the answer is a no-brainer. Choose an LCD projector! LCD projectors will constantly show bright, colourful images with fewer image errors. If you desire to learn more about LCD technology in more detail, see this fantastic resource website: Explore 3LCD. If you have any additional questions, go to Projector Central and send me an email.

Jonathan King is the sales and marketing manager at Projector Central, Australia’s leading online provider for projectors. Brisbane-based, Projector Central has been serving Australia for 15 years. For data projectors in Brisbane and Interactive Whiteboards, contact Projector Central today.