Projectors: LCD Verses DLP (The downfall of DLP technology)
The most common question customers ask when acquiring a new projector for the home, office, or classroom is: will I take an LCD projector or a DLP projector? LCD, short for ‘liquid crystal device’ and DLP, an acronym for ‘digital light processing’ are the two commonplace projector imaging technologies. With so many different brands and models available, it can be difficult for consumers to choose between those technologies. It comes down to the fact that LCD projectors offer better image quality and colour accuracy. The next part of this article will tell you why DLP projectors struggle with reproducing an equal level of image quality.
Imagine a set of blinds in your house covering 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. Such is exactly how an LCD projector operates. Each pixel works like an individual shutter on a set of blinds to either allow light through or to block it. DLP on the other hand is created 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 point when the projector is turned on to when the picture reaches your screen is absolutely significant 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 project the coloured light to 3 individual LCD panels. The 3 LCD panels create the elements of the image by shining each pixel on and off. The pixels are then combined in a glass prism to send the projector image. A significant point to understad about LCD projectors is that all three colours are directed onto your projected surface all at the same time. The way a DLP projector works is vastly different and even how an image looks is not the same. With DLP, white light from the lamp is directed through a rotating colour wheel with transparent red, blue and green segments, at speeds up to 11,000 rpm/s. This approach to forming an image creates a sequence of red, blue and green light. The millions of micro mirrors described above reflect the coloured light on the pixels to form the image elements. The elements of the image are projected in sequence on the screen, one colour at a time. The viewer’s eyes will then combine each coloured element of the image into the complete image. From LCD projectors, all colours are available all the time to offer the best brightness and spectacular colour accuracy. In DLP, only one colour is available at any given time, causing lower colour brightness and accuracy. Some developers have put a white segment for the colour wheel to improve all over brightness, but this goes and damages colour accuracy.
I hear in forums all the time that DLP provides a higher contrast ratio and as such must be superior. 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 system is able to produce. DLP projectors do possess high contrast specifications compared to a majority of LCD projectors. Initially, this must be a plus, however, in reality, the true black level is determined by the ambient light in the room when the projector is utilised. Do not be fooled by contrast specifications on websites and in brochures.
When the content you plan to view includes moving images, DLP projection technology can also have image errors, or ‘artifacts’. The most often seen artifact that a DLP projector displays with moving images is colour break up. Colour break up is to be expected in DLP systems because moving images keep changing between the time red, blue and green colours are shone. LCD projectors do not have this characteristic because the colours are sent at once. DLP manufacturers have formed 3DLP solutions using 3 chips to solve the colour break up problem, but the cost of these projectors make them hardly practical for the majority of businesses and consumers.
Another difference between LCD and DLP is how they make up for the refractive qualities of light. Remember back to high school science, and remember when they taught you how different colours of light refract different amounts when directed through the same lens. The downside with DLP projectors is that they use the one same panel with the same lens to project Red, Blue and Green. All 3 colours are obviously different and refract light in a different way. Often with a DLP projector, an extra yellow colour will show above and an extra blue will come through below an image as simple as a single black line. During manufacturing LCD projectors can be adjusted to reduce these effects on the projected image, as each colour is refracted on separate LCD panels.
The one true buy point (excluding price) with going with a DLP projector is its smaller size and weight. However, this is only relevant with regard to transporting the device and has to be traded off against the image plusses of LCD projectors. If the outcome of the picture quality is crucial to you, then the solution is simple. Go with an LCD projector! LCD projectors will constantly create bright, colourful images with fewer image imperfections. If you want to find out more about LCD technology in more detail, check out this spectacular 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 leading online store for projectors. Brisbane-based, Projector Central has served Australia for 15 years. For data projectors in Brisbane and Interactive Whiteboards, contact Projector Central today.