Projectors: LCD Verses DLP (The downfall of DLP technology)
The most common question customers ask when looking for a new projector for the home, office, or classroom is: should I get an LCD projector or a DLP projector? LCD, which stands for ‘liquid crystal device’ and DLP, standing for ‘digital light processing’ are the two most popular projector imaging technologies. With so many different brands and different types available, it can be confusing for customers to pick between those technologies. The simple fact of the matter is that LCD projectors give better image quality and colour accuracy. The article below will tell you why DLP projectors struggle with reproducing a comparable standard of image quality.
Visualise a set of blinds in your room on 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. Such is exactly how an LCD projector functions. Each pixel functions like a single shutter on a set of blinds to either allow 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 operates to either reflect light or block it.
How the light source is processed from the point when the projector switches on to when the picture reaches your screen is absolutely important for image quality, brightness and colour accuracy. LCD projectors process white light from the lamp by separating it into red, blue and green components, by three mirrors which send 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 simultaneously processed in a glass prism to deliver the projector image. A point to realise about LCD projectors is that all three colours are delivered onto your projected surface all at the same time. The way a DLP projector runs is vastly different and even the final product of 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 approach to projecting 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 cast in sequence on the screen, one colour at a time. The viewer’s eyes will then pull together each coloured element of the image into the whole image. Using LCD projectors, all colours are available all the time to offer high brightness and great colour accuracy. In DLP, only one colour is available at a time, and so resulting in lower colour brightness and accuracy. Some developers have added a white segment for the colour wheel to improve overall brightness, but this goes and degrades colour accuracy.
I read in forums all the time that DLP provides a higher contrast ratio and as such must be better. For those who are unaware, 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 capable of producing. DLP projectors do possess high contrast specifications in comparison to the majority of LCD projectors. At one glance, this appears to be a plus, however, in truth, the true black level is determined by the ambient light in the room where the projector is used. Do not be fooled by contrast specifications on websites and in brochures.
When the content you want to bring to life has moving images, DLP projection technology also has image errors, or ‘artifacts’. The most often seen artifact that a DLP projector creates with moving images is colour break up. Colour break up is to be expected in DLP systems because moving images change between the time red, blue and green colours are shone. LCD projectors do not have this problem because the colours are delivered simultaneously. DLP builders have formed 3DLP solutions using 3 chips to fix the colour break up issue, but the cost of these projectors make them hardly practical for many businesses and consumers.
Another differentiation between LCD and DLP is how they balance for the refractive qualities of light. Jump back to high school science, and recall when they taught you how the different colours of light refract varied amounts when passing 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 not the same and refract light at different levels. Generally with a DLP projector, a superfluous yellow colour will show above and a superfluous blue will appear below an image as simple as a lone black line. During manufacturing LCD projectors can be set to minimize these effects on the projected image, because each colour is projected on isolated LCD panels.
The isolated real plus (excluding price) with choosing a DLP projector is its smaller overall size and weight. However, this is only relevant with regard to mobility and has to be traded off against the image plusses of LCD projectors. If overall picture quality is important to you, then the solution is no-brainer. Take an LCD projector! LCD projectors will always produce bright, colourful images with fewer image blips. If you want to ask more about LCD technology in more detail, have a look at this fabulous resource website: Explore 3LCD. If you have any more questions, get onto Projector Central and send me an email.
Jonathan King is the sales and marketing manager at Projector Central, Australia’s number one online shop for projectors. Brisbane based, Projector Central has serviced Australia for 15 years. For data projectors in the Gold Coast and Interactive Whiteboards, contact Projector Central today.
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