Projectors: LCD Verses DLP (The downfall of DLP technology)
The most typical question customers ask when purchasing a new projector for the home, office, or classroom is: do I buy an LCD projector or a DLP projector? LCD, which stands for ‘liquid crystal device’ and DLP, an acronym for ‘digital light processing’ are the two commonplace projector imaging technologies. With so many different brands and different types available, it can be confusing for customers to pick between the two technologies. It comes down to the fact that LCD projectors offer far better image quality and colour accuracy. The following article explains why DLP projectors struggle with bringing up the same level of image quality.
Imagine a set of blinds in your room for your bedroom window. By pulling on a rod you can turn the shutters open or closed, according to whether you want to let light in or not. That is exactly how an LCD projector functions. Each pixel functions like a single shutter on a set of blinds to either pass light through or to block it. DLP on the other hand is constructed of millions of microscopic mirrors or ‘pixel elements’ as the professionals 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 switched on to when the image reaches your screen is extremely significant with regard to image quality, brightness and colour accuracy. LCD projectors project white light from the lamp by splitting 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 cast the elements of the image by processing each pixel on and off. The pixels are then combined in a glass prism to send the projector image. Something important to understad about LCD projectors is that all three colours are directed onto your projector screen all at the same time. The way a DLP projector runs is very different and even the produced image looks is not the same. With DLP, white light from the lamp is projected through a rotating 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 mentioned above reflect the coloured light on the pixels to produce the image elements. The elements of the image are displayed in sequence on the screen, one colour at a time. The viewer’s vision will then draw each coloured element of the image into a complete image. With LCD projectors, all colours are available all the time to create the best brightness and great colour accuracy. In DLP, only one colour is available at any given time, resulting in lower colour brightness and accuracy. Some DLP developers have included a white segment for the colour wheel to improve brightness overall, but this further lessens colour accuracy.
I see in forums all the time that DLP has a higher contrast ratio and ergo must be better quality. For those who don’t know, 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 compared to the majority of LCD projectors. At a glance, this can seem to be a plus, however, in truth, the true black level is determined by the ambient light in the room where the projector is being used. Do not be hoodwinked by contrast specifications on websites and in brochures.
When the content you plan to bring to life includes moving images, DLP projection technology also creates image errors, or ‘artifacts’. The most commonplace 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 change position between the time red, blue and green colours are displayed. LCD projectors do not have this downside because all colours are sent with the others. DLP builders have formed 3DLP solutions using 3 chips to resolve the colour break up problem, but the expense of these projectors make them impractical for the majority of businesses and consumers.
Another difference between LCD and DLP is how they compensate for the refractive qualities of light. Take yourself back to high school science, and recall when they taught you how the different colours of light refract differing amounts when directed through the same lens. The downside with DLP projectors is that they have the one same panel for the same lens to project Red, Blue and Green. All 3 colours are obviously different and refract light at different levels. Most of the time with a DLP projector, some yellow colour will appear above and some blue will come through below an image as simple as a lone black line. While being built LCD projectors can be fixed to reduce these effects on the projected image, as each colour is refracted on isolated LCD panels.
The sole true buy point (excluding price) with going with a DLP projector is its smaller total size and weight. However, this is only relevant in regard to mobility and must be traded off against the image benefits of LCD projectors. If resulting picture quality is vital to you, then the choice is easy. Choose an LCD projector! LCD projectors will constantly create bright, colourful images with fewer image blips. 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, get onto Projector Central and send me an email.
Jonathan King is the sales and marketing manager at Projector Central, Australia’s top online shop for projectors. Based in Brisbane, 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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