Projectors: LCD Verses DLP (The downfall of DLP technology)
The most common question heard when purchasing a new projector for the home, office, or classroom is: should I purchase an LCD projector or a DLP projector? LCD, short 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 challenging for customers to make a decision between the two technologies. Ultimately LCD projectors have far better image quality and colour accuracy. The article below will explain why DLP projectors struggle with creating the same standard of image quality.
Think of a set of blinds in your household on your bedroom window. By pulling on a rod you can make the shutters open or closed, according to if you want to let light in or not. And that is exactly how an LCD projector behaves. Each pixel operates like its own shutter on a set of blinds to either shine light through or to block it. DLP on the other hand is formed of millions of microscopic mirrors or ‘pixel elements’ as the professionals 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 is turned on to when the content reaches your screen is vitally 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 direct the coloured light to 3 separate LCD panels. The 3 LCD panels make the elements of the image by turning each pixel on and off. The pixels are then meshed in a glass prism to form the projector image. An important point to realise about LCD projectors is that all three colours are sent onto your screen all at once. The way a DLP projector works is very different and even how an image appears is not the same. With DLP, white light from the lamp is processed through a spinning colour wheel with transparent red, blue and green segments, at speeds up to 11,000 rpm/s. This method of projecting an image creates a sequence of red, blue and green light. The millions of micro mirrors as mentioned above reflect the coloured light on the pixels to produce the image elements. The elements of the image are displayed in sequence on the screen, one colour at a time. The viewer’s vision will then combine each coloured element of the image into the single total image. From 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 any given time, resulting in lower colour brightness and accuracy. Some developers have placed a white segment in the colour wheel to improve brightness generally, but this then detracts from colour accuracy.
I hear in forums all the time that DLP offers a higher contrast ratio and thus must be superior quality. For those who are uncertain, 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 producing. DLP projectors do have high contrast specifications in comparison to many LCD projectors. At a glance, this appears to be a benefit, however, in reality, 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 project includes moving images, DLP projection technology can also have image marks, or ‘artifacts’. The most commonplace artifact that a DLP projector shows with moving images is colour break up. Colour break up is to be expected in DLP systems because moving images change position between the time red, blue and green colours are projected. LCD projectors do not have this problem because the colours are projected simultaneously. DLP builders have developed 3DLP solutions using 3 chips to fix the colour break up artifacts, but the expense of these projectors make them almost impossible for the large part of businesses and consumers.
Another differentiation between LCD and DLP is how they make up for the refractive qualities of light. Jump back to high school science, and 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 utilise the one same panel for the same lens to project Red, Blue and Green. All 3 colours are obviously different and refract light in different ways. Generally with a DLP projector, a spill of yellow colour will come through above and an extra blue will appear below an image containing something as simple as a single black line. During manufacturing LCD projectors can be adjusted to minimize these effects on the projected image, as each colour is projected on a separate LCD panels.
The isolated veritable plus (excluding price) with taking a DLP projector is its overall smaller size and weight. However, this is only relevant in regard to transport and cannot be traded off against the image advantages of LCD projectors. If the outcome of the picture quality is important to you, then the solution is easy. Choose an LCD projector! LCD projectors will definitely show bright, colourful images with fewer image errors. If you wish to learn more about LCD technology in more detail, have a gander at this fantastic resource website: Explore 3LCD. If you have any more questions, go to Projector Central and send me an email.
Jonathan King is the sales and marketing manager of Projector Central, Australia’s premier online shop 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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