Projectors: LCD Verses DLP (The downfall of DLP technology)
The typical question customers ask when acquiring a new projector for the home, office, or classroom is: should I take an LCD projector or a DLP projector? LCD, short for ‘liquid crystal device’ and DLP, short for ‘digital light processing’ are the two top projector imaging technologies. With so many company brands and types available, it can be challenging for the buyer to decide between both technologies. It comes down to the fact that LCD projectors offer superior image quality and colour accuracy. The article below explains why DLP projectors struggle with reproducing a similar rate of image quality.
Visualise a set of blinds in your room over your bedroom window. By pulling 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 works. Each pixel functions like a single 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 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 at which the projector is switched on to when the image reaches your screen is absolutely important in regard 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 project the coloured light to 3 stand alone LCD panels. The 3 LCD panels make the elements of the image by shining each pixel on and off. The pixels are then projected in a glass prism to form the projector image. Something to realise about LCD projectors is that all three colours are projected onto your projector screen all at the same time. The way a DLP projector runs is totally different and even how an image shows up 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 method of making 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 create the image elements. The elements of the image are cast in sequence on the screen, one colour at a time. The viewer’s vision will then pull together each coloured element of the image into a single full image. With LCD projectors, all colours are available all the time to offer high brightness and superb colour accuracy. In DLP, only one colour is available at once, causing lower colour brightness and accuracy. Some DLP developers have included a white segment for the colour wheel to improve brightness generally, but this further detracts from colour accuracy.
I read in forums all the time that DLP provides 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 system is capable of producing. DLP projectors do possess high contrast specifications compared to a majority of LCD projectors. At one glance, this must be a plus, however, in reality, the true black level is determined by the ambient light in the room while the projector is used. Do not be duped by contrast specifications on websites and in brochures.
When the content you are trying to view needs moving images, DLP projection technology can also have image marks, or ‘artifacts’. The most common artifact that a DLP projector forms with moving images is colour break up. Colour break up is unavoidable in DLP systems because moving images change between the time red, blue and green colours are pulled up. LCD projectors do not have this disadvantage because all colours are sent simultaneously. DLP manufacturers have created 3DLP solutions using 3 chips to resolve the colour break up problem, but the cost of these projectors make them not practical for many businesses and consumers.
Another differentiation between LCD and DLP is how they balance for the refractive qualities of light. Think back to high school science, and they taught you how the various colours of light refract various amounts when passing through the same lens. The disadvantage with DLP projectors is that they take the one same panel and the same lens to project Red, Blue and Green. All 3 colours are obviously different and refract light at different levels. Often with a DLP projector, a superfluous yellow colour will come through above and some extra blue will come up below an image containing something as simple as a straight black line. In manufacturing LCD projectors can be adapted to take away these effects on the projected image, because each colour is directed on its own LCD panels.
The sole true benefit (excluding price) with picking a DLP projector is its smaller overall size and weight. However, this is only relevant for mobility and cannot be traded off against the image advantages of LCD projectors. If resulting picture quality is crucial to you, then the answer is a no-brainer. Go with an LCD projector! LCD projectors will definitely make bright, colourful images with fewer image errors. If you need to learn more about LCD technology in more detail, see this spectacular resource website: Explore 3LCD. If you have any other questions, go to Projector Central and send me an email.
Jonathan King is the sales and marketing manager with Projector Central, Australia’s premier online retailer for projectors. Brisbane-based, Projector Central has been servicing Australia for 15 years. For data projectors in Brisbane and Interactive Whiteboards, contact Projector Central today.
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