Projectors: LCD Verses DLP (The downfall of DLP technology)
The common question heard when buying a new projector for the home, office, or classroom is: will I purchase an LCD projector or a DLP projector? LCD, short for ‘liquid crystal device’ and DLP, standing for ‘digital light processing’ are the two most common projector imaging technologies. With so many business brands and types available, it can be challenging for clients to decide between the two technologies. Ultimately LCD projectors provide far better image quality and colour accuracy. The next paragraph tells you why DLP projectors struggle with projecting a similar rate of image quality.
Imagine a set of blinds in your house covering your bedroom window. By pulling on a rod you can have the shutters open or closed, according to if you want to let light in or not. And that is exactly how an LCD projector works. Each pixel operates like a single shutter on a set of blinds to either pass light through or to block it. DLP on the other hand is created 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 when the projector is turned on to when the picture reaches your screen is extremely important 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 direct 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 form the projector image. Something important to understad about LCD projectors is that all three colours are sent onto your projected surface at once. The way a DLP projector operates is vastly different and even the final product of how an image appears is not the same. With DLP, white light from the lamp is projected 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 casts a sequence of red, blue and green light. The millions of micro mirrors as described 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 eye will then combine each coloured element of the image into the single complete image. With LCD projectors, all colours are available all the time to create top brightness and superb colour accuracy. In DLP, only one colour is available at any given time, resulting in lower colour brightness and accuracy. Some manufacturers have put a white segment in the colour wheel to improve general brightness, but this further degrades colour accuracy.
I hear in forums all the time that DLP has a higher contrast ratio and as such must be superior. 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 offer high contrast specifications compared to most LCD projectors. At one glance, this seems to be a benefit, however, in real life, the true black level is determined by the ambient light in the room while the projector is being used. Do not be tricked by contrast specifications on websites and in brochures.
When the content you are trying to project includes moving images, DLP projection technology also creates image errors, or ‘artifacts’. The most common artifact that a DLP projector shows with moving images is colour break up. Colour break up is incontrovertible in DLP systems because moving images change position between the time red, blue and green colours are shone. LCD projectors do not have this problem because all colours are delivered simultaneously. DLP manufacturers have formed 3DLP solutions using 3 chips to answer the colour break up problem, but the price tag of these projectors make them not practical for many businesses and consumers.
Another difference between LCD and DLP is how they compensate for the refractive qualities of light. Think back to high school science, and remember when they taught you how the different colours of light refract various amounts when directed through the same lens. The downfall with DLP projectors is that they utilise the one same panel and the same lens to project Red, Blue and Green. All 3 colours are not the same and refract light in different ways. Often with a DLP projector, some 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. In building LCD projectors can be fixed to reduce these effects on the projected image, as each colour is projected on its own LCD panels.
The one true benefit (excluding price) with buying a DLP projector is its smaller overall size and weight. However, this is only relevant to transport and has to be traded off against the image plusses of LCD projectors. If overall picture quality is vital to you, then the decision is simple. Go with an LCD projector! LCD projectors will constantly produce bright, colourful images with fewer image imperfections. If you want to know more about LCD technology in more detail, see this fabulous resource website: Explore 3LCD. If you have any persisting questions, jump onto Projector Central and send me an email.
Jonathan King is the sales and marketing manager with Projector Central, Australia’s top online store for projectors. Brisbane-based, Projector Central has serviced Australia for 15 years. For data projectors in the Gold Coast and Interactive Whiteboards, contact Projector Central today.