Projectors: LCD Verses DLP (The downfall of DLP technology)
The common question that is asked when looking for a new projector for the home, office, or classroom is: will I purchase an LCD projector or a DLP projector? LCD, which stands for ‘liquid crystal device’ and DLP, standing for ‘digital light processing’ are the two top projector imaging technologies. With so many different brands and types available, it can be challenging for clients to make a choice between these technologies. The fact is that LCD projectors give far better image quality and colour accuracy. The following article will tell you why DLP projectors struggle with bringing up an equal standard of image quality.
Visualise a set of blinds in your room covering your bedroom window. By a twist of 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 operates. Each pixel functions like an individual shutter on a set of blinds to either send light through or to block it. DLP on the other hand is constructed of millions of microscopic mirrors or ‘pixel elements’ as the experts 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 image reaches your screen is extremely important for 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 send the coloured light to 3 individual LCD panels. The 3 LCD panels make the elements of the image by processing each pixel on and off. The pixels are then projected in a glass prism to deliver the projector image. An important point to remember about LCD projectors is that all three colours are projected onto your screen all at the same time. The way a DLP projector operates is vastly different and even how an image looks is not the same. With DLP, white light from the lamp is sent through a turning colour wheel with transparent red, blue and green segments, at speeds up to 11,000 rpm/s. This approach to projecting an image casts a sequence of red, blue and green light. The millions of micro mirrors as mentioned above reflect the coloured light on the pixels to create the image elements. The elements of the image are projected in sequence on the screen, one colour at a time. The viewer’s vision will then combine each coloured element of the image into a complete image. Using LCD projectors, all colours are available all the time to create top brightness and great colour accuracy. In DLP, only one colour is available at once, causing lower colour brightness and accuracy. Some designers have added a white segment for the colour wheel to improve general brightness, but this goes and damages colour accuracy.
I read in forums all the time that DLP provides a higher contrast ratio and as such must be better 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. DLP projectors do provide high contrast specifications compared to many LCD projectors. At a 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 in use. Do not be hoodwinked by contrast specifications on websites and in brochures.
When the content you plan to project has moving images, DLP projection technology can also create image errors, or ‘artifacts’. The most commonplace artifact that a DLP projector creates with moving images is colour break up. Colour break up is inherent in DLP systems because moving images change up between the time red, blue and green colours are displayed. LCD projectors do not have this disadvantage because every colour is sent at the same time. DLP developers have developed 3DLP solutions using 3 chips to fix the colour break up problem, but the cost of these projectors make them not practical for the majority of businesses and consumers.
Another difference between LCD and DLP is how they balance for the refractive qualities of light. Take yourself back to high school science, and recall how the various colours of light refract varied amounts when projected through the same lens. The disadvantage with DLP projectors is that they have the one same panel for the same lens to project Red, Blue and Green. All 3 colours are different and refract light at different levels. Usually with a DLP projector, an extra yellow colour will come through above and a superfluous blue will appear below an image of something as simple as a straight black line. In building LCD projectors can be adjusted to minimize these effects on the projected image, because each colour is projected on isolated LCD panels.
The isolated real plus (excluding price) with deciding on a DLP projector is its overall smaller size and weight. However, this is only relevant with regard to transport and must be traded off against the image plusses of LCD projectors. If the outcome of the picture quality is vital to you, then the choice is easy. Take an LCD projector! LCD projectors will constantly make bright, colourful images with fewer image blips. If you need to find out more about LCD technology in more detail, check out this tremendous 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 premier online provider for projectors. Brisbane-based, Projector Central has served Australia for 15 years. For data projectors in the Gold Coast and Interactive Whiteboards, contact Projector Central today.
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