Projectors: LCD Verses DLP (The downfall of DLP technology)
The common question asked 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, standing for ‘digital light processing’ are the two top projector imaging technologies. With so many business brands and types available, it can be difficult for customers to make a choice between those technologies. Ultimately LCD projectors provide far better image quality and colour accuracy. The following article explains why DLP projectors struggle with bringing up a comparable level of image quality.
Visualise a set of blinds in your household for your bedroom window. By pulling on a rod you can have the shutters open or closed, depending on if you want to let light in or not. Such is exactly how an LCD projector functions. Each pixel operates like its own shutter on a set of blinds to either shine light through or to block it. DLP on the other hand is constructed of millions of microscopic mirrors or ‘pixel elements’ as pros like to call them. Each pixel element works to either reflect light or block it.
How the light source is processed from the point when the projector turns on to when the image reaches your screen is vitally significant to image quality, brightness and colour accuracy. LCD projectors shine white light from the lamp by dividing it into red, blue and green components, by three mirrors which send the coloured light to 3 individual LCD panels. The 3 LCD panels make the elements of the image by turning each pixel on and off. The pixels are then simultaneously processed in a glass prism to send the projector image. An important point to know about LCD projectors is that all three colours are projected onto your projected surface all at once. The way a DLP projector operates is widely different and even the produced image comes out is not the same. With DLP, white light from the lamp is directed through a turning colour wheel with transparent red, blue and green segments, at speeds up to 11,000 rpm/s. This approach to creating an image forms 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 sent in sequence on the screen, one colour at a time. The viewer’s vision will then draw each coloured element of the image into the total image. With LCD projectors, all colours are available all the time to offer the highest brightness and spectacular colour accuracy. In DLP, just one colour is available at once, and so causing lower colour brightness and accuracy. Some manufacturers have included a white segment in the colour wheel to improve overall brightness, but this also detracts from colour accuracy.
I hear in forums all the time that DLP gives a higher contrast ratio and as such must be better quality. 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 provide high contrast specifications as compared to many LCD projectors. Initially, this seems to be an advantage, however, in the real world, the true black level is determined by the ambient light in the room when the projector is in use. Do not be tricked by contrast specifications on websites and in brochures.
When the content you wish to view needs moving images, DLP projection technology also has image marks, or ‘artifacts’. The most typical artifact that a DLP projector displays with moving images is colour break up. Colour break up is inherent in DLP systems because moving images change between the time red, blue and green colours are shone. LCD projectors do not have this characteristic because all the colours are processed at once. DLP manufacturers have come up with 3DLP solutions using 3 chips to resolve the colour break up problem, but the price of these projectors make them hardly practical for the majority of businesses and consumers.
Another differentiation between LCD and DLP is how they balance for the refractive qualities of light. Remember back to high school science, and remember how various colours of light refract differing amounts when projected through the same lens. The downfall with DLP projectors is that they utilise 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. Usually with a DLP projector, some extra yellow colour will come through above and a spill of blue will come up below an image as simple as a single black line. In manufacturing LCD projectors can be adapted to reduce these effects on the projected image, because each colour is directed on its own LCD panels.
The only actual buy point (excluding price) with deciding on a DLP projector is its smaller total size and weight. However, this is only relevant to portability and cannot be traded off against the image advantages of LCD projectors. If overall picture quality is important to you, then the solution is a no-brainer. Take an LCD projector! LCD projectors will always produce bright, colourful images with fewer image errors. If you need to know more about LCD technology in more detail, have a look at this tremendous resource website: Explore 3LCD. If you have any other questions, get onto Projector Central and send me an email.
Jonathan King is the sales and marketing manager with Projector Central, Australia’s top online retailer 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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