Projectors: LCD Verses DLP (The downfall of DLP technology)
The common question customers ask when buying a new projector for the home, office, or classroom is: will I take an LCD projector or a DLP projector? LCD, standing for ‘liquid crystal device’ and DLP, an acronym for ‘digital light processing’ are the two most popular projector imaging technologies. With so many company brands and models available, it can be confusing for the buyer to make a decision between those technologies. Ultimately LCD projectors give far better image quality and colour accuracy. The next paragraph explains why DLP projectors struggle with creating a comparable grade of image quality.
It’s like a set of blinds in your house on your bedroom window. With the twist of a rod you can make the shutters open or closed, according to if you want to let light in or not. Such is exactly how an LCD projector works. Each pixel operates like a single 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 operates to either reflect light or block it.
How the light source is processed from when the projector turns on to when the content reaches your screen is ultimately significant to image quality, brightness and colour accuracy. LCD projectors direct 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 create the elements of the image by turning each pixel on and off. The pixels are then projected in a glass prism to send the projector image. Something to know about LCD projectors is that all three colours are sent onto your wall all at the same time. The way a DLP projector operates is totally different and even how an image looks 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 method of 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 create the image elements. The elements of the image are projected in sequence on the screen, one colour at a time. The viewer’s eye will then pull together each coloured element of the image into a single whole image. From LCD projectors, all colours are available all the time to deliver top brightness and great colour accuracy. In DLP, only one colour is available at any given time, resulting in lower colour brightness and accuracy. Some developers have added a white segment for the colour wheel to improve brightness overall, but this then damages colour accuracy.
I find in forums all the time that DLP has a higher contrast ratio and therefore must be superior. 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 machine is capable of. DLP projectors do offer high contrast specifications as compared to most LCD projectors. At a glance, this appears to be an advantage, 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 fooled by contrast specifications on websites and in brochures.
When the content you are trying to view includes moving images, DLP projection technology can also have image errors, or ‘artifacts’. The most common artifact that a DLP projector displays with moving images is colour break up. Colour break up is unavoidable in DLP systems because moving images change position between the time red, blue and green colours are displayed. LCD projectors do not have this downside because every colour is sent at once. DLP builders have come up with 3DLP solutions using 3 chips to resolve the colour break up artifacts, but the cost of these projectors make them hardly practical for the majority of businesses and consumers.
Another point of difference between LCD and DLP is how they match the balance for the refractive qualities of light. Think back to high school science, and recall how various colours of light refract various amounts when projected through the same lens. The problem with DLP projectors is that they utilise the one same panel for the same lens to project Red, Blue and Green. All 3 colours are obviously not the same and refract light differently. Usually with a DLP projector, some extra yellow colour will be projected above and a superfluous blue will show below an image containing something as simple as a straight black line. While being built LCD projectors can be set to take away these effects on the projected image, as each colour is projected on separate LCD panels.
The one real advantage (excluding price) with deciding on a DLP projector is its smaller overall size and weight. However, this is only relevant for mobility and needs to be traded off against the image benefits of LCD projectors. If overall picture quality is important to you, then the answer is a no-brainer. Take an LCD projector! LCD projectors will consistently produce bright, colourful images with fewer image mistakes. If you want to know more about LCD technology in more detail, have a gander at this fabulous resource website: Explore 3LCD. If you have any additional questions, go to Projector Central and send me an email.
Jonathan King is the sales and marketing manager for Projector Central, Australia’s top online provider for projectors. Brisbane-based, Projector Central has been serving Australia for 15 years. For data projectors in the Gold Coast and Interactive Whiteboards, contact Projector Central today.
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