Projectors: LCD Verses DLP (The downfall of DLP technology)
The typical question that is asked when buying a new projector for the home, office, or classroom is: should I buy an LCD projector or a DLP projector? LCD, standing for ‘liquid crystal device’ and DLP, which stands for ‘digital light processing’ are the two most common projector imaging technologies. With so many business brands and different types available, it can be challenging for customers to decide between the two technologies. The fact is that LCD projectors offer superior image quality and colour accuracy. The article below will tell you why DLP projectors struggle with bringing up a comparable grade of image quality.
Think of a set of blinds in your house on your bedroom window. By a twist of a rod you can have the shutters open or closed, depending on whether you want to let light in or not. Such is exactly how an LCD projector functions. Each pixel functions like a unique 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 operates to either reflect light or block it.
How the light source is processed from the time the projector turns on to when the picture reaches your screen is vitally significant for 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 direct the coloured light to 3 individual LCD panels. The 3 LCD panels create the elements of the image by switching each pixel on and off. The pixels are then combined in a glass prism to create the projector image. A point to remember about LCD projectors is that all three colours are sent onto your wall at the same time. The way a DLP projector works is vastly different and even how an image comes out 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 making 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 create the image elements. The elements of the image are displayed 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 a single full image. In LCD projectors, all colours are available all the time to offer the highest brightness and spectacular colour accuracy. In DLP, only one colour is available at any given time, and so causing lower colour brightness and accuracy. Some DLP developers have included a white segment in the colour wheel to improve all over brightness, but this then lessens colour accuracy.
I see in forums all the time that DLP provides a higher contrast ratio and ergo must be better. 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 producing. DLP projectors do possess high contrast specifications compared to many LCD projectors. At a glance, this can seem to be a benefit, however, in reality, the true black level is determined by the ambient light in the room where the projector is being used. Do not be hoodwinked by contrast specifications on websites and in brochures.
When the content you plan to view requires moving images, DLP projection technology can also have image errors, or ‘artifacts’. The most common artifact that a DLP projector shows 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 shone. LCD projectors do not have this problem because all the colours are sent simultaneously. DLP manufacturers have created 3DLP solutions using 3 chips to resolve the colour break up error, but the price of these projectors make them hardly practical for many businesses and consumers.
Another variance between LCD and DLP is how they balance for the refractive qualities of light. Jump back to high school science, and they taught you how various colours of light refract differing amounts when passing through the same lens. The disadvantage with DLP projectors is that they use the one same panel with the same lens to project Red, Blue and Green. All 3 colours are not the same and refract light in a different way. Most of the time with a DLP projector, an extra yellow colour will come through above and a superfluous blue will come up below an image of something as simple as a single black line. During manufacturing LCD projectors can be adapted to take away these effects on the projected image, because each colour is refracted on separate LCD panels.
The one actual benefit (excluding price) with choosing a DLP projector is its smaller size and weight. However, this is only relevant in regard to transporting the device and cannot be traded off against the image plusses of LCD projectors. If the outcome of the picture quality is crucial to you, then the choice is easy. Go with an LCD projector! LCD projectors will definitely make bright, colourful images with fewer image errors. If you need to ask more about LCD technology in more detail, see this spectacular 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 of Projector Central, Australia’s premier 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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