The most typical question heard when acquiring a new projector for the home, office, or classroom is: would I purchase an LCD projector or a DLP projector? LCD, an acronym for ‘liquid crystal device’ and DLP, an acronym for ‘digital light processing’ are the two most common projector imaging technologies. With so many brands and different types available, it can be challenging for consumers to pick between both technologies. Ultimately LCD projectors offer far superior image quality and colour accuracy. The following article tells you why DLP projectors struggle with reproducing a comparable level of image quality.
Imagine a set of blinds in your household for your bedroom window. With the twist of a rod you can have the shutters open or closed, depending on if you want to let light in or not. And such is exactly how an LCD projector functions. Each pixel operates like a single shutter on a set of blinds to either send light through or to block it. DLP on the other hand is formed 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 point at which the projector switches on to when the content reaches your screen is ultimately significant with regard to 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 transfer the coloured light to 3 stand alone LCD panels. The 3 LCD panels cast the elements of the image by switching each pixel on and off. The pixels are then projected in a glass prism to send the projector image. Something to realise about LCD projectors is that all three colours are delivered onto your screen at the same time. The way a DLP projector operates is very different and even how an image comes out is not the same. With DLP, white light from the lamp is sent through a turning colour wheel with transparent red, blue and green segments, at speeds up to 11,000 rpm/s. This approach to forming an image forms a sequence of red, blue and green light. The millions of micro mirrors described above reflect the coloured light on the pixels to construct 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 a single full image. Using LCD projectors, all colours are available all the time to deliver the best brightness and fantastic colour accuracy. In DLP, only one colour is available at any given time, and so resulting in lower colour brightness and accuracy. Some designers have put a white segment in the colour wheel to improve brightness generally, but this also damages colour accuracy.
I find in forums all the time that DLP has a higher contrast ratio and thus must be superior. For those who are 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 projector is capable of. DLP projectors do offer high contrast specifications as compared to a majority of LCD projectors. At first glance, this must be a plus, however, in truth, the true black level is determined by the ambient light in the room in which the projector is utilised. Do not be duped by contrast specifications on websites and in brochures.
When the content you want to see has moving images, DLP projection technology also has image marks, or ‘artifacts’. The most common artifact that a DLP projector creates with moving images is colour break up. Colour break up is to be expected 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 characteristic because all the colours are delivered simultaneously. DLP designers have come up with 3DLP solutions using 3 chips to answer the colour break up error, but the cost of these projectors make them almost impossible for most businesses and consumers.
Another difference between LCD and DLP is how they compensate for the refractive qualities of light. Jump back to high school science, and remember when they taught you how the different colours of light refract different amounts when projected through the same lens. The downside with DLP projectors is that they use the one same panel with 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, some extra yellow colour will show above and a superfluous blue will come up below an image containing something as simple as a lone black line. During manufacturing LCD projectors can be adjusted to minimize these effects on the projected image, as each colour is directed on separate LCD panels.
The isolated true advantage (excluding price) with deciding on a DLP projector is its smaller 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 overall picture quality is important to you, then the choice is no-brainer. Go with an LCD projector! LCD projectors will consistently produce bright, colourful images with fewer image blips. If you want to find out more about LCD technology in more detail, see this fantastic resource website: Explore 3LCD. If you have any persisting questions, go to Projector Central and send me an email.
Jonathan King is the sales and marketing manager of 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 Brisbane and Interactive Whiteboards, contact Projector Central today.
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