Projectors: LCD Verses DLP (The downfall of DLP technology)
The typical question customers ask when looking for a new projector for the home, office, or classroom is: should I purchase an LCD projector or a DLP projector? LCD, which stands for ‘liquid crystal device’ and DLP, an acronym for ‘digital light processing’ are the two most popular projector imaging technologies. With so many business brands and different models available, it can be overwhelming for the buyer to make a decision between the two technologies. It comes down to the fact that LCD projectors have better image quality and colour accuracy. The following article explains why DLP projectors struggle with reproducing a comparable rate of image quality.
Think of a set of blinds in your house covering your bedroom window. By pulling a rod you can turn the shutters open or closed, depending on if you want to let light in or not. That is exactly how an LCD projector behaves. Each pixel works like a single shutter on a set of blinds to either pass light through or to block it. DLP on the other hand is made up of millions of microscopic mirrors or ‘pixel elements’ as professionals like to call them. Each pixel element functions to either reflect light or block it.
How the light source is processed from the point at which the projector is switched on to when the image reaches your screen is absolutely important for 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 transfer the coloured light to 3 separate 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 send the projector image. An important point to realise about LCD projectors is that all three colours are delivered onto your 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 projected through a turning colour wheel with transparent red, blue and green segments, at speeds up to 11,000 rpm/s. This method of making 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 construct 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 the single complete image. With LCD projectors, all colours are available all the time to create the best brightness and fantastic colour accuracy. In DLP, only one colour is available at a time, causing lower colour brightness and accuracy. Some DLP manufacturers have included a white segment for the colour wheel to improve brightness generally, but this also damages colour accuracy.
I hear in forums all the time that DLP gives 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 technology is capable of. DLP projectors do provide high contrast specifications compared to a majority of LCD projectors. At one glance, this must be an advantage, however, in real life, the true black level is determined by the ambient light in the room in which the projector is being used. Do not be duped by contrast specifications on websites and in brochures.
When the content you are trying to view has moving images, DLP projection technology also has image imperfections, or ‘artifacts’. The most often seen artifact that a DLP projector shows with moving images is colour break up. Colour break up is incontrovertible in DLP systems because moving images change position between the time red, blue and green colours are projected. LCD projectors do not have this characteristic because every colour is delivered at once. DLP developers have created 3DLP solutions using 3 chips to solve the colour break up artifacts, but the cost of these projectors make them almost impossible for most businesses and consumers.
Another point of difference between LCD and DLP is how they match the balance for the refractive qualities of light. Remember back to high school science, and they taught you how different colours of light refract differing amounts when shone through the same lens. The downside 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 in different ways. Most of the time with a DLP projector, an extra yellow colour will show above and some blue will show below an image as simple as a straight black line. During manufacturing LCD projectors can be adjusted to minimize these effects on the projected image, as each colour is directed on isolated LCD panels.
The sole real buy point (excluding price) with deciding on a DLP projector is its overall smaller size and weight. However, this is only relevant to transport and cannot be traded off against the image benefits of LCD projectors. If overall picture quality is crucial to you, then the solution is easy. Choose an LCD projector! LCD projectors will always show bright, colourful images with fewer image blips. If you desire to know more about LCD technology in more detail, check out this spectacular resource website: Explore 3LCD. If you have any additional questions, get onto Projector Central and send me an email.
Jonathan King is the sales and marketing manager of Projector Central, Australia’s leading online shop for projectors. Brisbane based, Projector Central has served Australia for 15 years. For data projectors in Brisbane and Interactive Whiteboards, contact Projector Central today.
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