Projectors: LCD Verses DLP (The downfall of DLP technology)
The typical question that is asked when looking for 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, an acronym for ‘digital light processing’ are the two top projector imaging technologies. With so many different brands and types available, it can be difficult for clients to pick between both technologies. Ultimately LCD projectors have far better image quality and colour accuracy. The next paragraph tells you why DLP projectors struggle with creating a comparable level of image quality.
Visualise a set of blinds in your household over 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. And this is exactly how an LCD projector behaves. Each pixel operates like an individual shutter on a set of blinds to either shine light through or to block it. DLP on the other hand is made up of millions of microscopic mirrors or ‘pixel elements’ as the pros like to call them. Each pixel element functions to either reflect light or block it.
How the light source is processed from the time the projector is turned on to when the picture reaches your screen is ultimately important for 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 send the coloured light to 3 separate LCD panels. The 3 LCD panels cast the elements of the image by shining each pixel on and off. The pixels are then meshed in a glass prism to send the projector image. A point to understad about LCD projectors is that all three colours are directed onto your projector screen simultaneously. The way a DLP projector functions is very different and even how an image looks is not the same. With DLP, white light from the lamp is processed through a turning colour wheel with transparent red, blue and green segments, at speeds up to 11,000 rpm/s. This approach to forming 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 sent in sequence on the screen, one colour at a time. The viewer’s eye will then draw each coloured element of the image into a single whole image. From LCD projectors, all colours are available all the time to deliver the top level of brightness and fantastic colour accuracy. In DLP, only one colour is available at once, causing lower colour brightness and accuracy. Some designers have put a white segment for the colour wheel to improve overall brightness, but this also damages colour accuracy.
I hear in forums all the time that DLP has a higher contrast ratio and as such must be superior. For those unaware, 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 possess high contrast specifications compared to most LCD projectors. At one glance, this appears to be a plus, however, in reality, the true black level is determined by the ambient light in the room when the projector is used. Do not be tricked by contrast specifications on websites and in brochures.
When the content you plan to project needs moving images, DLP projection technology can also have image errors, 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 up between the time red, blue and green colours are displayed. LCD projectors do not have this downside because all the colours are sent with the others. DLP designers have developed 3DLP solutions using 3 chips to fix the colour break up error, but the price of these projectors make them impractical for many 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 when they taught you how different colours of light refract varied amounts when directed through the same lens. The disadvantage with DLP projectors is that they have 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. Most of the time with a DLP projector, a superfluous yellow colour will come up above and a superfluous blue will come through below an image of something as simple as a single black line. In building LCD projectors can be fixed to minimize these effects on the projected image, because each colour is directed on its own LCD panels.
The isolated veritable advantage (excluding price) with deciding on a DLP projector is its overall smaller size and weight. However, this is only relevant in regard to transporting the device and needs to be traded off against the image advantages of LCD projectors. If overall picture quality is vital to you, then the choice is no-brainer. Take an LCD projector! LCD projectors will consistently show bright, colourful images with fewer image mistakes. If you want to know more about LCD technology in more detail, check out this fantastic resource website: Explore 3LCD. If you have any additional questions, get onto Projector Central and send me an email.
Jonathan King is the sales and marketing manager at Projector Central, Australia’s number one online shop for projectors. Brisbane-based, Projector Central has served Australia for 15 years. For data projectors in Brisbane and Interactive Whiteboards, contact Projector Central today.