Projectors: LCD Verses DLP (The downfall of DLP technology)
The most typical question asked when acquiring 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, which stands for ‘digital light processing’ are the two most common projector imaging technologies. With so many different brands and different types available, it can be challenging for the buyer to decide between the two technologies. The simple fact of the matter is that LCD projectors offer far better image quality and colour accuracy. The following article tells you why DLP projectors struggle with reproducing an equal grade of image quality.
Visualise a set of blinds in your room covering your bedroom window. By a twist of a rod you can make the shutters open or closed, according to whether you want to let light in or not. And this is exactly how an LCD projector works. Each pixel functions like its own shutter on a set of blinds to either pass light through or to block it. DLP on the other hand is created of millions of microscopic mirrors or ‘pixel elements’ as pros like to call them. Each pixel element operates to either reflect light or block it.
How the light source is processed from the point at which the projector switches on to when the picture reaches your screen is ultimately important in regard to image quality, brightness and colour accuracy. LCD projectors direct white light from the lamp by cutting it into red, blue and green components, by three mirrors which send the coloured light to 3 individual LCD panels. The 3 LCD panels form the elements of the image by shining each pixel on and off. The pixels are then meshed in a glass prism to deliver the projector image. Something to realise 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 very different and even the produced image looks is not the same. With DLP, white light from the lamp is sent through a rotating colour wheel with transparent red, blue and green segments, at speeds up to 11,000 rpm/s. This method of 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 displayed 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 the total image. From LCD projectors, all colours are available all the time to deliver the best brightness and spectacular colour accuracy. In DLP, just one colour is available at a time, resulting in lower colour brightness and accuracy. Some DLP designers have put a white segment in the colour wheel to improve brightness generally, but this goes and lessens colour accuracy.
I read in forums all the time that DLP offers a higher contrast ratio and therefore must be superior. For those 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 projector is able to produce. DLP projectors do possess high contrast specifications when compared to a majority of LCD projectors. Initially, this can seem to be a plus, however, in real life, the true black level is determined by the ambient light in the room where the projector is being utilised. Do not be duped by contrast specifications on websites and in brochures.
When the content you are trying to see has moving images, DLP projection technology can also have image marks, or ‘artifacts’. The most often seen artifact that a DLP projector forms 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 disadvantage because every colour is sent at once. DLP developers have created 3DLP solutions using 3 chips to fix the colour break up artifacts, but the cost of these projectors make them almost impossible for most businesses and consumers.
Another differentiation between LCD and DLP is how they make up for the refractive qualities of light. Think back to high school science, and recall how various colours of light refract various amounts when passing 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 not the same and refract light in a different way. Often with a DLP projector, some yellow colour will come up above and a superfluous blue will come through below an image of something as simple as a single black line. While being built LCD projectors can be set to remove these effects on the projected image, because each colour is projected on separate LCD panels.
The only true buy point (excluding price) with taking a DLP projector is its smaller size and weight. However, this is only relevant with regard to portability and must be traded off against the image superiority of LCD projectors. If overall picture quality is vital to you, then the solution is no-brainer. Go with an LCD projector! LCD projectors will consistently make bright, colourful images with fewer image mistakes. If you wish to ask more about LCD technology in more detail, have a gander at this tremendous resource website: Explore 3LCD. If you have any additional questions, jump onto Projector Central and send me an email.
Jonathan King is the sales and marketing manager of Projector Central, Australia’s leading online store for projectors. Based in Brisbane, Projector Central has served Australia for 15 years. For data projectors in Brisbane and Interactive Whiteboards, contact Projector Central today.
