Projectors: LCD Verses DLP (The downfall of DLP technology)
The most common question customers ask when buying a new projector for the home, office, or classroom is: will I take an LCD projector or a DLP projector? LCD, an acronym for ‘liquid crystal device’ and DLP, which stands for ‘digital light processing’ are the two most popular projector imaging technologies. With so many different brands and types available, it can be difficult for consumers to choose between both technologies. The simple fact of the matter is that LCD projectors have superior image quality and colour accuracy. The next part of this article will tell you why DLP projectors struggle with reproducing a similar level of image quality.
Imagine a set of blinds in your room for your bedroom window. By a twist of a rod you can have the shutters open or closed, depending on whether you want to let light in or not. And this is exactly how an LCD projector functions. Each pixel operates like a unique shutter on a set of blinds to either allow 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 functions to either reflect light or block it.
How the light source is processed from when the projector turns on to when the content reaches your screen is extremely significant for image quality, brightness and colour accuracy. LCD projectors process white light from the lamp by separating it into red, blue and green components, by three mirrors which send the coloured light to 3 stand alone LCD panels. The 3 LCD panels cast the elements of the image by shining each pixel on and off. The pixels are then simultaneously processed in a glass prism to send the projector image. Something to know about LCD projectors is that all three colours are delivered onto your projected surface all at once. The way a DLP projector runs is very different and even the way an image comes out is not the same. With DLP, white light from the lamp is directed through a spinning colour wheel with transparent red, blue and green segments, at speeds up to 11,000 rpm/s. This method of creating an image casts a sequence of red, blue and green light. The millions of micro mirrors described above reflect the coloured light on the pixels to produce the image elements. The elements of the image are cast in sequence on the screen, one colour at a time. The viewer’s eyes will then pull together each coloured element of the image into a single whole image. From LCD projectors, all colours are available all the time to form the best brightness and great colour accuracy. In DLP, only one colour is available at a time, resulting in lower colour brightness and accuracy. Some designers have included a white segment into the colour wheel to improve brightness generally, but this then detracts from colour accuracy.
I read in forums all the time that DLP gives a higher contrast ratio and as such must be better. 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. DLP projectors do have high contrast specifications as compared to most LCD projectors. Initially, 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 being used. Do not be fooled 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 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 problem because all the colours are delivered with the others. DLP developers have created 3DLP solutions using 3 chips to solve the colour break up artifacts, but the price tag of these projectors make them not practical for the large part of businesses and consumers.
Another point of difference between LCD and DLP is how they balance for the refractive qualities of light. Think back to high school science, and remember when they taught you how the various colours of light refract different amounts when passing through the same lens. The problem with DLP projectors is that they take 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 at different levels. Often with a DLP projector, some extra yellow colour will come up above and a spill of blue will be projected below an image containing something as simple as a single black line. In manufacturing LCD projectors can be set to take away these effects on the projected image, as each colour is directed on its own LCD panels.
The isolated true plus (excluding price) with taking a DLP projector is its overall smaller size and weight. However, this is only relevant to transport and must be traded off against the image benefits of LCD projectors. If resulting picture quality is crucial to you, then the choice is simple. Go with an LCD projector! LCD projectors will consistently show bright, colourful images with fewer image mistakes. If you wish to ask more about LCD technology in more detail, have a look at this spectacular resource website: Explore 3LCD. If you have any more questions, visit Projector Central and send me an email.
Jonathan King is the sales and marketing manager of Projector Central, Australia’s leading online store for projectors. Brisbane based, Projector Central has served Australia for 15 years. For data projectors in the Gold Coast and Interactive Whiteboards, contact Projector Central today.
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