Projectors: LCD Verses DLP (The downfall of DLP technology)
The most typical question heard when buying a new projector for the home, office, or classroom is: would I buy an LCD projector or a DLP projector? LCD, standing for ‘liquid crystal device’ and DLP, standing for ‘digital light processing’ are the two top projector imaging technologies. With so many company brands and types available, it can be challenging for the buyer to choose between both technologies. The simple fact of the matter is that LCD projectors give far better image quality and colour accuracy. The next part of this article will explain why DLP projectors struggle with creating a similar standard of image quality.
Think of a set of blinds in your room covering your bedroom window. By a twist of a rod you can have the shutters open or closed, according to whether you want to let light in or not. And such is exactly how an LCD projector operates. Each pixel works like a single shutter on a set of blinds to either shine light through or to block it. DLP on the other hand is created 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 point when the projector is switched on to when the image reaches your screen is ultimately significant 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 project the coloured light to 3 different LCD panels. The 3 LCD panels create 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. An important point to understad about LCD projectors is that all three colours are sent onto your screen all at once. The way a DLP projector works is vastly different and even the way an image shows up is not the same. With DLP, white light from the lamp is projected through a spinning colour wheel with transparent red, blue and green segments, at speeds up to 11,000 rpm/s. This method of forming 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 construct the image elements. The elements of the image are sent in sequence on the screen, one colour at a time. The viewer’s eyes will then pull together each coloured element of the image into the full image. From LCD projectors, all colours are available all the time to deliver top brightness and spectacular colour accuracy. In DLP, only one colour is available at a time, causing lower colour brightness and accuracy. Some designers have placed a white segment in the colour wheel to improve all over brightness, but this also damages colour accuracy.
I find in forums all the time that DLP gives a higher contrast ratio and ergo must be superior quality. For those who are 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 system is capable of producing. DLP projectors do offer high contrast specifications as compared to many LCD projectors. Initially, this seems to be an advantage, however, in reality, the true black level is determined by the ambient light in the room when the projector is in use. Do not be duped by contrast specifications on websites and in brochures.
When the content you want to view needs moving images, DLP projection technology can also create image marks, or ‘artifacts’. The most often seen artifact that a DLP projector shows with moving images is colour break up. Colour break up is unavoidable in DLP systems because moving images keep changing between the time red, blue and green colours are pulled up. LCD projectors do not have this downside because the colours are processed with the others. DLP manufacturers have developed 3DLP solutions using 3 chips to solve the colour break up issue, but the price tag of these projectors make them impractical for the majority of businesses and consumers.
Another point of difference between LCD and DLP is how they make up for the refractive qualities of light. Remember back to high school science, and remember when they taught you how the different colours of light refract differing amounts when passing through the same lens. The downside with DLP projectors is that they use the one same panel and the same lens to project Red, Blue and Green. All 3 colours are not the same and refract light in different ways. Usually with a DLP projector, a spill of yellow colour will be projected above and some blue will be projected below an image containing something as simple as a single black line. While being built LCD projectors can be adjusted to reduce these effects on the projected image, because each colour is processed on isolated LCD panels.
The only real plus (excluding price) with picking a DLP projector is its overall smaller size and weight. However, this is only relevant with regard to transporting the device and needs to be traded off against the image benefits of LCD projectors. If resulting picture quality is crucial to you, then the solution is simple. Go for an LCD projector! LCD projectors will always make bright, colourful images with fewer image errors. If you want to know more about LCD technology in more detail, have a gander at this fantastic resource website: Explore 3LCD. If you have any persisting questions, get onto Projector Central and send me an email.
Jonathan King is the sales and marketing manager for Projector Central, Australia’s top online provider for projectors. Brisbane based, 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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