Projectors: LCD Verses DLP (The downfall of DLP technology)
The most typical question that is asked when looking for a new projector for the home, office, or classroom is: would I get an LCD projector or a DLP projector? LCD, an acronym for ‘liquid crystal device’ and DLP, which stands for ‘digital light processing’ are the two most common projector imaging technologies. With so many company brands and models available, it can be overwhelming for clients to decide between these technologies. It comes down to the fact that LCD projectors give far superior image quality and colour accuracy. The following article explains why DLP projectors struggle with creating an equal standard of image quality.
Visualise a set of blinds in your home for your bedroom window. With the twist of a rod you can turn 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 its own 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 professionals like to call them. Each pixel element works to either reflect light or block it.
How the light source is processed from the time the projector is turned on to when the content reaches your screen is ultimately significant 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 send the coloured light to 3 different LCD panels. The 3 LCD panels form 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 remember about LCD projectors is that all three colours are delivered onto your projector screen simultaneously. The way a DLP projector runs is very different and even the final product of how an image looks is not the same. With DLP, white light from the lamp is projected 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 requires a sequence of red, blue and green light. The millions of micro mirrors as mentioned above reflect the coloured light on the pixels to construct the image elements. The elements of the image are sent in sequence on the screen, one colour at a time. The viewer’s eyes will then draw each coloured element of the image into the single total image. In LCD projectors, all colours are available all the time to create high brightness and fantastic colour accuracy. In DLP, just one colour is available at any given time, resulting in lower colour brightness and accuracy. Some DLP developers have placed a white segment for the colour wheel to improve general brightness, but this then degrades colour accuracy.
I see in forums all the time that DLP provides a higher contrast ratio and ergo must be superior quality. For those who are 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 technology is capable of producing. DLP projectors do have high contrast specifications as 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 where the projector is used. Do not be tricked by contrast specifications on websites and in brochures.
When the content you wish to bring to life requires moving images, DLP projection technology also creates image errors, or ‘artifacts’. The most common artifact that a DLP projector creates 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 displayed. LCD projectors do not have this downside because the colours are processed with the others. DLP builders have formed 3DLP solutions using 3 chips to fix the colour break up issue, but the expense of these projectors make them hardly practical for the majority of businesses and consumers.
Another differentiation between LCD and DLP is how they make up for the refractive qualities of light. Think back to high school science, and recall how the different colours of light refract different amounts when passing through the same lens. The disadvantage 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 in a different way. Most of the time with a DLP projector, some yellow colour will show above and an extra blue will come up below something as simple as a lone black line. While being built LCD projectors can be set to remove these effects on the projected image, because each colour is refracted on separate LCD panels.
The one true advantage (excluding price) with going with a DLP projector is its smaller overall size and weight. However, this is only relevant in regard to portability and needs to be traded off against the image superiority of LCD projectors. If the result of the picture quality is vital to you, then the solution is a no-brainer. Go with an LCD projector! LCD projectors will consistently create bright, colourful images with fewer image mistakes. If you want to ask more about LCD technology in more detail, check out this fantastic resource website: Explore 3LCD. If you have any further questions, jump onto Projector Central and send me an email.
Jonathan King is the sales and marketing manager with Projector Central, Australia’s leading online provider for projectors. Brisbane based, Projector Central has serviced Australia for 15 years. For data projectors in Brisbane and Interactive Whiteboards, contact Projector Central today.
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