Projectors: LCD Verses DLP (The downfall of DLP technology)
The most typical question asked when acquiring a new projector for the home, office, or classroom is: would I take an LCD projector or a DLP projector? LCD, which stands for ‘liquid crystal device’ and DLP, short for ‘digital light processing’ are the two most common projector imaging technologies. With so many business brands and different types available, it can be difficult for consumers to choose between both technologies. Ultimately LCD projectors have far better image quality and colour accuracy. The following article will tell you why DLP projectors struggle with bringing up a comparable rate of image quality.
Imagine a set of blinds in your house on your bedroom window. With the twist of a rod you can turn the shutters open or closed, according to if you want to let light in or not. This is exactly how an LCD projector behaves. Each pixel works like a unique shutter on a set of blinds to either allow light through or to block it. DLP on the other hand is formed 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 when the projector switches on to when the picture reaches your screen is vitally important for image quality, brightness and colour accuracy. LCD projectors project white light from the lamp by dividing it into red, blue and green components, by three mirrors which project the coloured light to 3 individual LCD panels. The 3 LCD panels create the elements of the image by turning each pixel on and off. The pixels are then combined in a glass prism to deliver the projector image. Something to understad about LCD projectors is that all three colours are delivered onto your screen simultaneously. The way a DLP projector operates is very different and even the final product of how an image shows up is not the same. With DLP, white light from the lamp is directed through a rotating 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 mentioned above reflect the coloured light on the pixels to create 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 put together each coloured element of the image into the single complete image. With LCD projectors, all colours are available all the time to offer the best 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 manufacturers have put a white segment in the colour wheel to improve general brightness, but this goes and detracts from colour accuracy.
I hear in forums all the time that DLP gives a higher contrast ratio and thus 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 projector is capable of. DLP projectors do possess high contrast specifications as compared to most LCD projectors. At first glance, this appears to 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 fooled by contrast specifications on websites and in brochures.
When the content you wish to view needs moving images, DLP projection technology also creates image errors, or ‘artifacts’. The most commonplace artifact that a DLP projector displays with moving images is colour break up. Colour break up is to be expected in DLP systems because moving images change position between the time red, blue and green colours are shone. LCD projectors do not have this characteristic because all colours are delivered with the others. DLP manufacturers have come up with 3DLP solutions using 3 chips to answer the colour break up error, 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. Take yourself back to high school science, and they taught you how different colours of light refract various amounts when shone through the same lens. The downside with DLP projectors is that they have 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 differently. Often with a DLP projector, a spill of yellow colour will come up above and some extra blue will appear below an image of something as simple as a single black line. In manufacturing LCD projectors can be adjusted to minimize these effects on the projected image, as each colour is refracted on its own LCD panels.
The only real buy point (excluding price) with taking a DLP projector is its smaller total size and weight. However, this is only relevant with regard to transporting the device and must be traded off against the image plusses of LCD projectors. If resulting picture quality is crucial to you, then the decision is a no-brainer. Choose an LCD projector! LCD projectors will definitely show bright, colourful images with fewer image errors. If you desire to know more about LCD technology in more detail, have a look at this tremendous 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 number one online shop for projectors. Brisbane based, Projector Central has been serving Australia for 15 years. For data projectors in the Gold Coast and Interactive Whiteboards, contact Projector Central today.
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