The most common question customers ask when acquiring a new projector for the home, office, or classroom is: will I buy 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 brands and different types available, it can be challenging for clients to decide between the two technologies. The fact is that LCD projectors have better image quality and colour accuracy. The article below will tell you why DLP projectors struggle with bringing up a similar grade of image quality.
Think of a set of blinds in your room covering your bedroom window. By pulling on a rod you can have the shutters open or closed, depending on if you want to let light in or not. This is exactly how an LCD projector behaves. Each pixel functions 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 is turned on to when the image reaches your screen is vitally important to image quality, brightness and colour accuracy. LCD projectors project white light from the lamp by separating it into red, blue and green components, by three mirrors which transfer the coloured light to 3 individual LCD panels. The 3 LCD panels form the elements of the image by processing each pixel on and off. The pixels are then meshed in a glass prism to send the projector image. A point to realise about LCD projectors is that all three colours are sent onto your screen at the same time. The way a DLP projector functions is very different and even the produced 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 approach to forming an image requires a sequence of red, blue and green light. The millions of micro mirrors mentioned above reflect the coloured light on the pixels to form the image elements. The elements of the image are sent 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 the complete image. From LCD projectors, all colours are available all the time to offer high brightness and spectacular colour accuracy. In DLP, only one colour is available at a time, and so resulting in lower colour brightness and accuracy. Some DLP designers have added a white segment for the colour wheel to improve brightness generally, but this then detracts from colour accuracy.
I hear in forums all the time that DLP offers a higher contrast ratio and thus must be better. For those unsure, 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. DLP projectors do offer high contrast specifications as compared to a majority of LCD projectors. At a glance, this seems to be a benefit, however, in the real world, the true black level is determined by the ambient light in the room in which the projector is utilised. Do not be tricked by contrast specifications on websites and in brochures.
When the content you wish to project includes moving images, DLP projection technology also creates image errors, or ‘artifacts’. The most often seen artifact that a DLP projector shows with moving images is colour break up. Colour break up is to be expected in DLP systems because moving images change up between the time red, blue and green colours are pulled up. LCD projectors do not have this problem because every colour is processed with the others. DLP manufacturers have formed 3DLP solutions using 3 chips to solve the colour break up problem, but the price of these projectors make them not practical for the majority of businesses and consumers.
Another difference between LCD and DLP is how they compensate for the refractive qualities of light. Remember back to high school science, and recall how the different colours of light refract varied amounts when passing through the same lens. The problem with DLP projectors is that they use the one same panel with the same lens to project Red, Blue and Green. All 3 colours are obviously not the same and refract light in different ways. Generally with a DLP projector, an extra yellow colour will come up above and some blue will show below an image of something as simple as a single black line. During manufacturing LCD projectors can be adapted to minimize these effects on the projected image, because each colour is refracted on isolated LCD panels.
The isolated real plus (excluding price) with deciding on a DLP projector is its smaller total size and weight. However, this is only relevant with regard to mobility and must be traded off against the image plusses of LCD projectors. If resulting picture quality is important to you, then the choice is easy. Choose an LCD projector! LCD projectors will constantly show bright, colourful images with fewer image imperfections. If you need to know more about LCD technology in more detail, check out this fabulous resource website: Explore 3LCD. If you have any persisting questions, go to Projector Central and send me an email.
Jonathan King is the sales and marketing manager for Projector Central, Australia’s number one online retailer for projectors. Brisbane based, Projector Central has been servicing Australia for 15 years. For data projectors in the Gold Coast and Interactive Whiteboards, contact Projector Central today.