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The most common question heard when buying a new projector for the home, office, or classroom is: do I buy an LCD projector or a DLP projector? LCD, short 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 models available, it can be confusing for clients to make a choice between those technologies. It comes down to the fact that LCD projectors offer far better image quality and colour accuracy. The following article will explain why DLP projectors struggle with projecting a similar rate of image quality.

Visualise a set of blinds in your home on your bedroom window. By pulling on a rod you can have the shutters open or closed, according to whether you want to let light in or not. That is exactly how an LCD projector operates. 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 constructed of millions of microscopic mirrors or ‘pixel elements’ as the professionals like to call them. Each pixel element works to either reflect light or block it.

How the light source is processed from the time the projector is turned on to when the image reaches your screen is extremely important for image quality, brightness and colour accuracy. LCD projectors project white light from the lamp by dividing it into red, blue and green components, by three mirrors which transfer the coloured light to 3 individual LCD panels. The 3 LCD panels cast the elements of the image by shining each pixel on and off. The pixels are then simultaneously processed in a glass prism to send the projector image. Something important to understad about LCD projectors is that all three colours are projected onto your projected surface all at once. The way a DLP projector works is vastly different and even the final product of how an image comes out is not the same. With DLP, white light from the lamp is projected through a turning colour wheel with transparent red, blue and green segments, at speeds up to 11,000 rpm/s. This way of making an image creates 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 combine each coloured element of the image into a single whole image. Using LCD projectors, all colours are available all the time to create the highest brightness and superb colour accuracy. In DLP, only one colour is available at any given time, and so causing lower colour brightness and accuracy. Some DLP designers have included a white segment for the colour wheel to improve overall brightness, but this goes and degrades colour accuracy.

I find in forums all the time that DLP gives a higher contrast ratio and thus must be superior. 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. DLP projectors do offer high contrast specifications in comparison to a majority of LCD projectors. Initially, this can seem to be a plus, however, in the real world, the true black level is determined by the ambient light in the room while the projector is utilised. Do not be hoodwinked by contrast specifications on websites and in brochures.

When the content you are trying to view requires moving images, DLP projection technology also creates image marks, or ‘artifacts’. The most common artifact that a DLP projector shows 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 shone. LCD projectors do not have this downside because the colours are sent at the same time. DLP developers have come up with 3DLP solutions using 3 chips to resolve the colour break up error, but the expense 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. Jump back to high school science, and remember how the different colours of light refract various amounts when passing through the same lens. The problem with DLP projectors is that they use the one same panel for the same lens to project Red, Blue and Green. All 3 colours are different and refract light at different levels. Usually with a DLP projector, a spill of yellow colour will come up above and some extra blue will come through below something as simple as a lone black line. In manufacturing LCD projectors can be adapted to minimize these effects on the projected image, as each colour is refracted on a separate LCD panels.

The one veritable plus (excluding price) with choosing a DLP projector is its smaller size and weight. However, this is only relevant with regard to transport and must be traded off against the image plusses of LCD projectors. If resulting picture quality is vital to you, then the solution is easy. Go with an LCD projector! LCD projectors will constantly produce bright, colourful images with fewer image blips. If you wish to find out more about LCD technology in more detail, check out this fantastic 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 number one online retailer 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.

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