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: would I buy an LCD projector or a DLP projector? LCD, which stands for ‘liquid crystal device’ and DLP, short for ‘digital light processing’ are the two most common projector imaging technologies. With so many business brands and types available, it can be overwhelming for consumers to make a choice between those technologies. Ultimately LCD projectors offer far better image quality and colour accuracy. The next part of this article explains why DLP projectors struggle with reproducing a comparable grade of image quality.
Think of a set of blinds in your house on your bedroom window. By pulling on a rod you can make the shutters open or closed, depending on if you want to let light in or not. And this is exactly how an LCD projector behaves. Each pixel functions like a unique shutter on a set of blinds to either send light through or to block it. DLP on the other hand is made up 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 the point when the projector is turned on to when the content reaches your screen is extremely important for image quality, brightness and colour accuracy. LCD projectors project white light from the lamp by dividing it into red, blue and green components, by three mirrors which transfer the coloured light to 3 individual LCD panels. The 3 LCD panels make the elements of the image by turning each pixel on and off. The pixels are then combined in a glass prism to deliver the projector image. A significant point to know about LCD projectors is that all three colours are sent onto your screen at the same time. The way a DLP projector works is vastly different and even how an image shows up is not the same. With DLP, white light from the lamp is directed through a turning colour wheel with transparent red, blue and green segments, at speeds up to 11,000 rpm/s. This method of making an image casts 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 cast in sequence on the screen, one colour at a time. The viewer’s vision will then pull together each coloured element of the image into the single whole image. From LCD projectors, all colours are available all the time to offer the highest brightness and great colour accuracy. In DLP, just one colour is available at any given time, and so resulting in lower colour brightness and accuracy. Some DLP designers have placed a white segment for the colour wheel to improve brightness overall, but this then degrades colour accuracy.
I find in forums all the time that DLP offers a higher contrast ratio and therefore must be better 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 offer high contrast specifications in comparison to the majority of LCD projectors. Initially, this appears to be an advantage, however, in truth, 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 want to project needs moving images, DLP projection technology also creates image marks, or ‘artifacts’. The most typical artifact that a DLP projector forms with moving images is colour break up. Colour break up is incontrovertible in DLP systems because moving images change up between the time red, blue and green colours are shone. LCD projectors do not have this characteristic because the colours are processed simultaneously. DLP builders have come up with 3DLP solutions using 3 chips to solve the colour break up artifacts, but the price tag of these projectors make them almost impossible for many businesses and consumers.
Another point of difference between LCD and DLP is how they make up for the refractive qualities of light. Remember back to high school science, and they taught you how the various colours of light refract differing amounts when shone through the same lens. The disadvantage with DLP projectors is that they utilise the one same panel and the same lens to project Red, Blue and Green. All 3 colours are obviously not the same and refract light in a different way. Most of the time with a DLP projector, an extra yellow colour will be projected above and a spill of blue will show below an image as simple as a single black line. During manufacturing LCD projectors can be set to reduce these effects on the projected image, because each colour is processed on its own LCD panels.
The sole veritable benefit (excluding price) with going with a DLP projector is its smaller total size and weight. However, this is only relevant for mobility and cannot be traded off against the image plusses of LCD projectors. If the result of the picture quality is important to you, then the answer is easy. Go with an LCD projector! LCD projectors will constantly make bright, colourful images with fewer image mistakes. If you want to find out more about LCD technology in more detail, see this spectacular resource website: Explore 3LCD. If you have any persisting questions, get onto Projector Central and send me an email.
Jonathan King is the sales and marketing manager for Projector Central, Australia’s leading online retailer for projectors. Brisbane-based, Projector Central has serviced Australia for 15 years. For data projectors in Brisbane and Interactive Whiteboards, contact Projector Central today.
