Projectors: LCD Verses DLP (The downfall of DLP technology)
The common 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, which stands for ‘digital light processing’ are the two top projector imaging technologies. With so many different brands and different types available, it can be difficult for the buyer to pick between those technologies. The simple fact of the matter is that LCD projectors provide far superior image quality and colour accuracy. The next part of this article explains why DLP projectors struggle with projecting the same level of image quality.
Visualise a set of blinds in your household 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. That is exactly how an LCD projector behaves. Each pixel operates like a single shutter on a set of blinds to either allow light through or to block it. DLP on the other hand is created of millions of microscopic mirrors or ‘pixel elements’ as the pros like to call them. Each pixel element operates to either reflect light or block it.
How the light source is processed from when the projector is turned on to when the content reaches your screen is extremely significant to image quality, brightness and colour accuracy. LCD projectors process white light from the lamp by splitting it into red, blue and green components, by three mirrors which send 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 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 all at the same time. The way a DLP projector works is widely different and even how an image comes out is not the same. With DLP, white light from the lamp is projected through a turning colour wheel with transparent red, blue and green segments, at speeds up to 11,000 rpm/s. This method of making an image requires 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 displayed in sequence on the screen, one colour at a time. The viewer’s eye will then draw each coloured element of the image into the single whole image. With LCD projectors, all colours are available all the time to form the top level of brightness and fantastic colour accuracy. In DLP, just one colour is available at a time, and so resulting in lower colour brightness and accuracy. Some manufacturers have included a white segment for the colour wheel to improve all over brightness, but this further detracts from colour accuracy.
I read in forums all the time that DLP offers a higher contrast ratio and ergo must be superior quality. For those uncertain, 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 producing. DLP projectors do offer high contrast specifications as compared to a majority of LCD projectors. At one glance, this can seem to be an advantage, however, in reality, the true black level is determined by the ambient light in the room while the projector is being utilised. Do not be duped by contrast specifications on websites and in brochures.
When the content you plan to project has moving images, DLP projection technology can also create image errors, or ‘artifacts’. The most typical 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 position between the time red, blue and green colours are displayed. LCD projectors do not have this downside because the colours are sent at once. DLP builders have come up with 3DLP solutions using 3 chips to fix the colour break up error, but the price of these projectors make them impractical for most businesses and consumers.
Another point of difference between LCD and DLP is how they balance for the refractive qualities of light. Take yourself back to high school science, and remember when they taught you how the various colours of light refract various amounts when directed through the same lens. The downfall with DLP projectors is that they have the one same panel with the same lens to project Red, Blue and Green. All 3 colours are different and refract light in different ways. Usually with a DLP projector, some yellow colour will show above and some blue will come through below something as simple as a lone black line. In manufacturing LCD projectors can be adjusted to remove these effects on the projected image, as each colour is processed on separate LCD panels.
The one true buy point (excluding price) with going with a DLP projector is its overall smaller size and weight. However, this is only relevant with regard to transporting the device and has to be traded off against the image plusses of LCD projectors. If resulting picture quality is important to you, then the solution is a no-brainer. Take an LCD projector! LCD projectors will always make bright, colourful images with fewer image imperfections. If you need to find out more about LCD technology in more detail, see this fabulous resource website: Explore 3LCD. If you have any additional questions, jump onto Projector Central and send me an email.
Jonathan King is the sales and marketing manager at Projector Central, Australia’s premier online provider for projectors. Brisbane-based, Projector Central has serviced Australia for 15 years. For data projectors in the Gold Coast and Interactive Whiteboards, contact Projector Central today.
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