Projectors: LCD Verses DLP (The downfall of DLP technology)
The typical question customers ask when purchasing a new projector for the home, office, or classroom is: do I take an LCD projector or a DLP projector? LCD, an acronym for ‘liquid crystal device’ and DLP, an acronym for ‘digital light processing’ are the two most common projector imaging technologies. With so many company brands and models available, it can be overwhelming for consumers to make a decision between these technologies. The simple fact of the matter is that LCD projectors offer far better image quality and colour accuracy. The next part of this article tells you why DLP projectors struggle with reproducing an equal grade of image quality.
Think of a set of blinds in your room covering your bedroom window. By a twist of a rod you can make the shutters open or closed, depending on if you want to let light in or not. And that is exactly how an LCD projector behaves. Each pixel functions like a single shutter on a set of blinds to either send light through or to block it. DLP on the other hand is made up of millions of microscopic mirrors or ‘pixel elements’ as pros like to call them. Each pixel element functions 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 picture reaches your screen is ultimately important to image quality, brightness and colour accuracy. LCD projectors project white light from the lamp by separating it into red, blue and green components, by three mirrors which transfer the coloured light to 3 stand alone LCD panels. The 3 LCD panels make the elements of the image by shining each pixel on and off. The pixels are then meshed in a glass prism to send the projector image. A significant point to remember about LCD projectors is that all three colours are delivered onto your projector screen simultaneously. The way a DLP projector functions is vastly different and even how an image looks is not the same. With DLP, white light from the lamp is sent through a spinning colour wheel with transparent red, blue and green segments, at speeds up to 11,000 rpm/s. This approach to creating an image requires a sequence of red, blue and green light. The millions of micro mirrors described above reflect the coloured light on the pixels to create the image elements. The elements of the image are projected in sequence on the screen, one colour at a time. The viewer’s vision will then put together each coloured element of the image into the complete image. From LCD projectors, all colours are available all the time to offer the highest brightness and fantastic colour accuracy. In DLP, just one colour is available at once, causing lower colour brightness and accuracy. Some designers have put a white segment in the colour wheel to improve brightness overall, but this goes and lessens colour accuracy.
I see in forums all the time that DLP provides a higher contrast ratio and as such must be superior quality. For those who do not 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 machine is able to produce. DLP projectors do offer high contrast specifications compared to the majority of LCD projectors. At a glance, this seems to be a plus, 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 fooled by contrast specifications on websites and in brochures.
When the content you wish to bring to life includes moving images, DLP projection technology also creates image errors, or ‘artifacts’. The most typical artifact that a DLP projector displays with moving images is colour break up. Colour break up is inherent in DLP systems because moving images change between the time red, blue and green colours are projected. LCD projectors do not have this characteristic because the colours are delivered simultaneously. DLP designers have come up with 3DLP solutions using 3 chips to fix the colour break up problem, but the cost of these projectors make them hardly practical for many businesses and consumers.
Another difference between LCD and DLP is how they balance for the refractive qualities of light. Take yourself back to high school science, and they taught you how the different colours of light refract differing 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 obviously not the same and refract light at different levels. Most of the time with a DLP projector, some extra yellow colour will be projected above and a spill of blue will show below an image as simple as a straight black line. In building LCD projectors can be set to minimize these effects on the projected image, because each colour is refracted on separate LCD panels.
The isolated true advantage (excluding price) with picking a DLP projector is its smaller size and weight. However, this is only relevant with regard to transporting the device and has to be traded off against the image plusses of LCD projectors. If overall picture quality is crucial to you, then the choice is easy. Go for an LCD projector! LCD projectors will always show bright, colourful images with fewer image imperfections. If you want to know more about LCD technology in more detail, see this fabulous resource website: Explore 3LCD. If you have any further questions, visit Projector Central and send me an email.
Jonathan King is the sales and marketing manager with Projector Central, Australia’s number one online store for projectors. Based in Brisbane, 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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