The most typical question that is asked when buying a new projector for the home, office, or classroom is: do I get an LCD projector or a DLP projector? LCD, an acronym for ‘liquid crystal device’ and DLP, standing for ‘digital light processing’ are the two commonplace projector imaging technologies. With so many different brands and types available, it can be challenging for customers to make a choice between both technologies. It comes down to the fact that LCD projectors provide far superior image quality and colour accuracy. The next part of this article explains why DLP projectors struggle with bringing up an equal standard of image quality.
It’s like a set of blinds in your house over your bedroom window. By pulling a rod you can make the shutters open or closed, depending on whether you want to let light in or not. This is exactly how an LCD projector operates. Each pixel works like its own shutter on a set of blinds to either send light through or to block it. DLP on the other hand is formed of millions of microscopic mirrors or ‘pixel elements’ as the professionals 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 switched on to when the image reaches your screen is ultimately important in 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 project the coloured light to 3 stand alone LCD panels. The 3 LCD panels cast the elements of the image by switching each pixel on and off. The pixels are then meshed in a glass prism to send the projector image. An important point to understad about LCD projectors is that all three colours are sent onto your screen simultaneously. The way a DLP projector runs is widely different and even the way an image appears is not the same. With DLP, white light from the lamp is sent through a rotating colour wheel with transparent red, blue and green segments, at speeds up to 11,000 rpm/s. This way of forming an image casts 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 sent in sequence on the screen, one colour at a time. The viewer’s eye will then draw each coloured element of the image into a full image. Using LCD projectors, all colours are available all the time to form the top level of brightness and superb colour accuracy. In DLP, only one colour is available at once, resulting in lower colour brightness and accuracy. Some DLP designers have added a white segment into the colour wheel to improve brightness overall, but this further degrades colour accuracy.
I hear in forums all the time that DLP offers a higher contrast ratio and ergo must be superior quality. For those who are 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 able to produce. DLP projectors do possess high contrast specifications in comparison to the majority of LCD projectors. At a glance, this appears to be a plus, however, in truth, the true black level is determined by the ambient light in the room when the projector is used. Do not be hoodwinked by contrast specifications on websites and in brochures.
When the content you plan to view has moving images, DLP projection technology also creates image imperfections, or ‘artifacts’. The most commonplace artifact that a DLP projector forms with moving images is colour break up. Colour break up is to be expected in DLP systems because moving images change between the time red, blue and green colours are displayed. LCD projectors do not have this problem because all the colours are projected with the others. DLP builders have created 3DLP solutions using 3 chips to fix the colour break up issue, but the cost of these projectors make them not practical for many businesses and consumers.
Another differentiation 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 projected through the same lens. The disadvantage 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 not the same and refract light at different levels. Generally with a DLP projector, some yellow colour will show above and some extra blue will appear below an image of something as simple as a straight black line. In manufacturing LCD projectors can be fixed to take away these effects on the projected image, because each colour is projected on separate LCD panels.
The isolated veritable buy point (excluding price) with going with a DLP projector is its smaller size and weight. However, this is only relevant in regard to portability and must be traded off against the image plusses of LCD projectors. If overall picture quality is important to you, then the choice is easy. Take an LCD projector! LCD projectors will constantly make bright, colourful images with fewer image mistakes. If you need to learn more about LCD technology in more detail, have a gander at this fantastic resource website: Explore 3LCD. If you have any persisting 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 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.
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