Projectors: LCD Verses DLP (The downfall of DLP technology)
The most common question customers ask when acquiring a new projector for the home, office, or classroom is: would I take an LCD projector or a DLP projector? LCD, which stands for ‘liquid crystal device’ and DLP, which stands for ‘digital light processing’ are the two most common projector imaging technologies. With so many brands and different models available, it can be difficult for customers to decide between both technologies. The fact is that LCD projectors provide superior image quality and colour accuracy. The following article tells you why DLP projectors struggle with reproducing a comparable rate of image quality.
It’s like a set of blinds in your house covering your bedroom window. By pulling a rod you can have the shutters open or closed, according to if you want to let light in or not. That is exactly how an LCD projector behaves. Each pixel functions like a unique shutter on a set of blinds to either allow light through or to block it. DLP on the other hand is formed of millions of microscopic mirrors or ‘pixel elements’ as 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 when the projector is turned on to when the content reaches your screen is ultimately important to 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 separate 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 deliver the projector image. Something important to realise about LCD projectors is that all three colours are delivered onto your projected surface all at the same time. The way a DLP projector operates is very different and even the way an image appears is not the same. With DLP, white light from the lamp is directed through a spinning 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 as described above reflect the coloured light on the pixels to produce the image elements. The elements of the image are projected in sequence on the screen, one colour at a time. The viewer’s eyes will then put together each coloured element of the image into the single whole image. In LCD projectors, all colours are available all the time to form the best brightness and superb colour accuracy. In DLP, just one colour is available at once, and so resulting in lower colour brightness and accuracy. Some DLP manufacturers have included a white segment for the colour wheel to improve brightness overall, but this then damages colour accuracy.
I see in forums all the time that DLP gives a higher contrast ratio and ergo must be better quality. 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 machine is capable of. DLP projectors do possess high contrast specifications compared to the majority of LCD projectors. At first glance, this can seem to be a plus, however, in truth, the true black level is determined by the ambient light in the room while the projector is being used. Do not be tricked by contrast specifications on websites and in brochures.
When the content you wish to see requires 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 incontrovertible in DLP systems because moving images change between the time red, blue and green colours are projected. LCD projectors do not have this downside because all colours are projected with the others. DLP manufacturers have created 3DLP solutions using 3 chips to solve the colour break up issue, but the price tag of these projectors make them impractical for most businesses and consumers.
Another point of difference between LCD and DLP is how they make up for the refractive qualities of light. Jump back to high school science, and recall how the various colours of light refract varied amounts when projected through the same lens. The disadvantage 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 in a different way. Most of the time with a DLP projector, a spill of yellow colour will come up above and some extra blue will be projected below an image of something as simple as a straight black line. In manufacturing LCD projectors can be adjusted to remove these effects on the projected image, as each colour is processed on isolated LCD panels.
The sole true benefit (excluding price) with buying a DLP projector is its smaller size and weight. However, this is only relevant to mobility and has to be traded off against the image benefits of LCD projectors. If the outcome of the picture quality is crucial to you, then the choice is no-brainer. Go with an LCD projector! LCD projectors will always show bright, colourful images with fewer image blips. If you want to learn more about LCD technology in more detail, have a gander at this spectacular resource website: Explore 3LCD. If you have any more questions, jump onto Projector Central and send me an email.
Jonathan King is the sales and marketing manager of Projector Central, Australia’s leading online provider for projectors. Based in Brisbane, 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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