Projectors: LCD Verses DLP (The downfall of DLP technology)
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The most typical question that is asked when looking for a new projector for the home, office, or classroom is: would I buy an LCD projector or a DLP projector? LCD, which stands for ‘liquid crystal device’ and DLP, short for ‘digital light processing’ are the two commonplace projector imaging technologies. With so many company brands and models available, it can be confusing for customers to decide between these technologies. It comes down to the fact that LCD projectors give better image quality and colour accuracy. The following article will explain why DLP projectors struggle with projecting the same grade of image quality.
Think of a set of blinds in your house over your bedroom window. By pulling on a rod you can make the shutters open or closed, depending on whether you want to let light in or not. This is exactly how an LCD projector functions. Each pixel works like an individual 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 the 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 at which the projector switches on to when the content reaches your screen is extremely significant for image quality, brightness and colour accuracy. LCD projectors process white light from the lamp by cutting it into red, blue and green components, by three mirrors which direct the coloured light to 3 individual LCD panels. The 3 LCD panels make the elements of the image by switching each pixel on and off. The pixels are then projected 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 projector screen all at the same time. The way a DLP projector operates is very different and even the produced image appears 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 creating 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 eyes will then combine each coloured element of the image into a single full image. From LCD projectors, all colours are available all the time to offer the highest brightness and great colour accuracy. In DLP, just one colour is available at a time, resulting in lower colour brightness and accuracy. Some designers have put a white segment into the colour wheel to improve brightness generally, but this then lessens colour accuracy.
I hear in forums all the time that DLP gives a higher contrast ratio and therefore must be superior. 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 when compared to a majority of LCD projectors. At first glance, this must be a plus, however, in real life, 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 wish to project has moving images, DLP projection technology can also have image marks, or ‘artifacts’. The most often seen artifact that a DLP projector displays with moving images is colour break up. Colour break up is incontrovertible in DLP systems because moving images change up between the time red, blue and green colours are shone. LCD projectors do not have this disadvantage because all the colours are processed at once. DLP builders have come up with 3DLP solutions using 3 chips to resolve the colour break up problem, but the price tag of these projectors make them not practical for many businesses and consumers.
Another differentiation between LCD and DLP is how they balance for the refractive qualities of light. Take yourself back to high school science, and recall when they taught you how various colours of light refract various amounts when directed through the same lens. The disadvantage 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 obviously not the same and refract light in different ways. Usually with a DLP projector, some yellow colour will be projected above and an extra blue will come up below an image as simple as a straight black line. During manufacturing LCD projectors can be set to reduce these effects on the projected image, as each colour is refracted on a separate LCD panels.
The one real benefit (excluding price) with going with 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 benefits of LCD projectors. If the result of the picture quality is important to you, then the answer is easy. Take an LCD projector! LCD projectors will consistently make bright, colourful images with fewer image errors. If you need to find out more about LCD technology in more detail, have a look at this spectacular resource website: Explore 3LCD. If you have any further questions, jump onto Projector Central and send me an email.
Jonathan King is the sales and marketing manager with Projector Central, Australia’s leading online shop for projectors. Brisbane-based, Projector Central has served Australia for 15 years. For data projectors in the Gold Coast and Interactive Whiteboards, contact Projector Central today.
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