Projectors: LCD Verses DLP (The downfall of DLP technology)
The common question that is asked when acquiring a new projector for the home, office, or classroom is: do I take an LCD projector or a DLP projector? LCD, which stands for ‘liquid crystal device’ and DLP, standing for ‘digital light processing’ are the two most popular projector imaging technologies. With so many company brands and models available, it can be confusing for customers to decide between the two technologies. The simple fact of the matter is that LCD projectors provide far better image quality and colour accuracy. The next paragraph explains why DLP projectors struggle with creating a similar level of image quality.
Imagine a set of blinds in your home over your bedroom window. By a twist of a rod you can make the shutters open or closed, depending on if you want to let light in or not. And such is exactly how an LCD projector behaves. Each pixel works like its own shutter on a set of blinds to either pass light through or to block it. DLP on the other hand is made up of millions of microscopic mirrors or ‘pixel elements’ as professionals like to call them. Each pixel element operates to either reflect light or block it.
How the light source is processed from the time the projector is switched on to when the picture reaches your screen is absolutely significant to image quality, brightness and colour accuracy. LCD projectors process 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 create the elements of the image by turning each pixel on and off. The pixels are then meshed in a glass prism to form the projector image. A significant point to understad about LCD projectors is that all three colours are directed onto your screen all at the same time. The way a DLP projector operates is widely different and even the way an image looks is not the same. With DLP, white light from the lamp is sent through a spinning colour wheel with transparent red, blue and green segments, at speeds up to 11,000 rpm/s. This method of projecting an image casts a sequence of red, blue and green light. The millions of micro mirrors as 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 combine each coloured element of the image into a single total image. From LCD projectors, all colours are available all the time to offer the highest brightness and fantastic colour accuracy. In DLP, just one colour is available at a time, and so resulting in lower colour brightness and accuracy. Some designers have added a white segment in the colour wheel to improve all over brightness, but this further detracts from colour accuracy.
I find in forums all the time that DLP offers a higher contrast ratio and thus must be superior. 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 projector is capable of producing. DLP projectors do possess high contrast specifications in comparison to many LCD projectors. At one glance, this must be a benefit, however, in truth, the true black level is determined by the ambient light in the room when the projector is being used. Do not be hoodwinked by contrast specifications on websites and in brochures.
When the content you want to bring to life needs moving images, DLP projection technology also has image imperfections, or ‘artifacts’. The most commonplace 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 position between the time red, blue and green colours are displayed. LCD projectors do not have this disadvantage because every colour is projected with the others. DLP designers have formed 3DLP solutions using 3 chips to answer the colour break up error, but the price of these projectors make them hardly practical for many businesses and consumers.
Another difference between LCD and DLP is how they match the balance for the refractive qualities of light. Jump back to high school science, and recall how various colours of light refract varied amounts when directed through the same lens. The downside with DLP projectors is that they use 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. Generally with a DLP projector, a spill of yellow colour will come through above and a superfluous blue will come up below an image of something as simple as a single black line. During manufacturing LCD projectors can be set to minimize these effects on the projected image, as each colour is directed on a separate LCD panels.
The sole veritable plus (excluding price) with buying a DLP projector is its smaller overall size and weight. However, this is only relevant with regard to mobility and needs to be traded off against the image plusses of LCD projectors. If resulting picture quality is vital to you, then the choice is easy. Take an LCD projector! LCD projectors will always create bright, colourful images with fewer image blips. If you wish to ask more about LCD technology in more detail, see this fabulous resource website: Explore 3LCD. If you have any further questions, get onto Projector Central and send me an email.
Jonathan King is the sales and marketing manager with Projector Central, Australia’s number one 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.