Projectors: LCD Verses DLP (The downfall of DLP technology)
The typical question that is asked when acquiring a new projector for the home, office, or classroom is: should I buy an LCD projector or a DLP projector? LCD, short for ‘liquid crystal device’ and DLP, short for ‘digital light processing’ are the two most popular projector imaging technologies. With so many brands and types available, it can be challenging for the buyer to make a choice between the two technologies. Ultimately LCD projectors give better image quality and colour accuracy. The next part of this article will explain why DLP projectors struggle with reproducing a comparable level of image quality.
Imagine a set of blinds in your household covering your bedroom window. By pulling 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 works. Each pixel operates like its own 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 time the projector is switched on to when the image reaches your screen is absolutely significant in regard to image quality, brightness and colour accuracy. LCD projectors project white light from the lamp by cutting it into red, blue and green components, by three mirrors which project the coloured light to 3 stand alone LCD panels. The 3 LCD panels form the elements of the image by processing each pixel on and off. The pixels are then combined in a glass prism to send the projector image. An important point to remember about LCD projectors is that all three colours are delivered onto your projector screen all at the same time. The way a DLP projector works is very different and even the way an image appears is not the same. With DLP, white light from the lamp is projected through a rotating colour wheel with transparent red, blue and green segments, at speeds up to 11,000 rpm/s. This method of making an image creates a sequence of red, blue and green light. The millions of micro mirrors mentioned above reflect the coloured light on the pixels to produce the image elements. The elements of the image are displayed in sequence on the screen, one colour at a time. The viewer’s eye will then pull together each coloured element of the image into a single total image. From LCD projectors, all colours are available all the time to create the best brightness and superb colour accuracy. In DLP, just one colour is available at any given time, causing lower colour brightness and accuracy. Some DLP manufacturers have placed a white segment into the colour wheel to improve brightness overall, but this goes and detracts from colour accuracy.
I read in forums all the time that DLP has a higher contrast ratio and ergo 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 system is capable of. DLP projectors do possess 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 while the projector is being utilised. Do not be hoodwinked by contrast specifications on websites and in brochures.
When the content you are trying to view has moving images, DLP projection technology can also have image imperfections, or ‘artifacts’. The most common artifact that a DLP projector forms with moving images is colour break up. Colour break up is to be expected in DLP systems because moving images change between the time red, blue and green colours are pulled up. LCD projectors do not have this downside because all colours are projected simultaneously. DLP developers have created 3DLP solutions using 3 chips to answer the colour break up problem, but the price of these projectors make them not practical for the majority of businesses and consumers.
Another difference between LCD and DLP is how they compensate for the refractive qualities of light. Remember back to high school science, and remember how the various colours of light refract different amounts when passing through the same lens. The downside with DLP projectors is that they utilise the one same panel for the same lens to project Red, Blue and Green. All 3 colours are not the same and refract light in different ways. Generally with a DLP projector, some extra yellow colour will be projected above and some blue will be projected below an image containing something as simple as a lone black line. During manufacturing LCD projectors can be adjusted to remove these effects on the projected image, as each colour is processed on separate LCD panels.
The sole real benefit (excluding price) with choosing a DLP projector is its smaller overall size and weight. However, this is only relevant with regard to portability and needs to be traded off against the image plusses of LCD projectors. If the result of the picture quality is important to you, then the decision is a no-brainer. Choose an LCD projector! LCD projectors will always show bright, colourful images with fewer image imperfections. If you wish to know more about LCD technology in more detail, have a look at this fantastic resource website: Explore 3LCD. If you have any persisting questions, visit Projector Central and send me an email.
Jonathan King is the sales and marketing manager with Projector Central, Australia’s top online provider 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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