Projectors: LCD Verses DLP (The downfall of DLP technology)
The most typical question heard when acquiring a new projector for the home, office, or classroom is: would I buy an LCD projector or a DLP projector? LCD, short for ‘liquid crystal device’ and DLP, which stands for ‘digital light processing’ are the two commonplace projector imaging technologies. With so many different brands and types available, it can be confusing for clients to pick between these technologies. Ultimately LCD projectors provide superior image quality and colour accuracy. The next part of this article tells you why DLP projectors struggle with reproducing an equal standard of image quality.
Imagine a set of blinds in your house on your bedroom window. By pulling a rod you can have the shutters open or closed, according to whether you want to let light in or not. That is exactly how an LCD projector behaves. Each pixel operates like an individual shutter on a set of blinds to either allow light through or to block it. DLP on the other hand is formed of millions of microscopic mirrors or ‘pixel elements’ as 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 switches on to when the image reaches your screen is absolutely important with regard to image quality, brightness and colour accuracy. LCD projectors shine white light from the lamp by cutting it into red, blue and green components, by three mirrors which transfer the coloured light to 3 stand alone LCD panels. The 3 LCD panels cast the elements of the image by switching each pixel on and off. The pixels are then projected in a glass prism to deliver the projector image. Something important to realise about LCD projectors is that all three colours are directed onto your projected surface all at the same time. The way a DLP projector works is totally different and even the way an image appears 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 way of forming an image casts a sequence of red, blue and green light. The millions of micro mirrors mentioned above reflect the coloured light on the pixels to create the image elements. The elements of the image are displayed 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 the single total image. Using LCD projectors, all colours are available all the time to create the best brightness and superb colour accuracy. In DLP, only one colour is available at once, resulting in lower colour brightness and accuracy. Some DLP manufacturers have included a white segment in the colour wheel to improve brightness overall, but this goes and damages colour accuracy.
I find in forums all the time that DLP has a higher contrast ratio and therefore must be better. 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 system is capable of. DLP projectors do possess high contrast specifications in comparison to a majority of LCD projectors. At a glance, this seems to be a plus, however, in truth, the true black level is determined by the ambient light in the room while the projector is utilised. Do not be tricked by contrast specifications on websites and in brochures.
When the content you are trying to view requires moving images, DLP projection technology can also create image imperfections, or ‘artifacts’. The most typical artifact that a DLP projector creates with moving images is colour break up. Colour break up is incontrovertible in DLP systems because moving images change between the time red, blue and green colours are pulled up. LCD projectors do not have this characteristic because all the colours are delivered with the others. DLP manufacturers have formed 3DLP solutions using 3 chips to answer the colour break up artifacts, but the cost of these projectors make them impractical for many businesses and consumers.
Another variance between LCD and DLP is how they balance for the refractive qualities of light. Remember back to high school science, and they taught you how the various colours of light refract different amounts when passing through the same lens. The downside 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 at different levels. Often with a DLP projector, an extra yellow colour will show above and a spill of blue will appear below an image as simple as a lone black line. In manufacturing LCD projectors can be set to minimize these effects on the projected image, as each colour is directed on separate LCD panels.
The only actual plus (excluding price) with buying a DLP projector is its overall smaller size and weight. However, this is only relevant for mobility and cannot be traded off against the image plusses of LCD projectors. If the result of the picture quality is crucial to you, then the solution is simple. Choose an LCD projector! LCD projectors will definitely show bright, colourful images with fewer image imperfections. If you need to know more about LCD technology in more detail, check out this tremendous 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 of Projector Central, Australia’s top online shop 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.