Projectors have many differentiating features, but the core technology they are built around can be divided into two main types, LCD (Liquid Crystal Display) and DLP (Digital Light Processing). The two technologies have both been around for long enough to be considered fully mature, and they each have individual merits so it is useful to understand the differences in order to make an informed purchasing decision.

LCD technology is the older of the two, but continues to occupy a strong position in the market in the face of strong competition from DLP. This is largely because the technology is so well established that manufacturers are able to benefit from the economies of scale that come with a system that has gained widespread acceptance. Because of this, a lot of manufacturers use LCD technology in their entry level and low to mid range devices as it allows them to build a well specified projector at a reasonable cost.

LCD projectors work by shining white light through three coloured LCD panels (red, green and blue) – the light from these panels is then combined and projected through a lens onto the screen to make up the complete full colour picture. LCD does not offer the best image quality on the market, but nevertheless the picture quality produced is perfectly adequate for general business usage and this, combined with low prices, has allowed LCD to continue performing favourably for most vendors. One of LCD’s strong points is that it allows for higher brightness, an important factor when displaying presentations in less than suitable lighting conditions. This means that you can get an LCD projector with a high brightness rating for less than you would pay for a comparably specified DLP device.

LCD technology has a couple of weak points. The image quality it delivers for moving images is poor in comparison to DLP devices. On an image projected by an LCD machine there will often be a noticeable gap between the individual pixels that make up the entire image. This produces what is known as ‘screen door effect’ since it is rather like looking at the image through the kind of net curtain mesh that screen doors are made from, and it is especially noticeable in video images.

The second area that LCD technology falls behind in is contrast ratio which, again, is largely a problem for people who want to project moving video or even still photographic images. Sharp’s Barton illustrates the point perfectly “In PowerPoint you would normally use a coloured wash background with different colour text and what have you, so contrast ratio is not so important, where you’ve got a video with some ninja dressed in black running across a black skyline contrast ratio becomes quite important.”

While it does not match up to DLP technology in some respects, LCD is stillcapable of offering image quality that is perfectly good enough for many practical applications and has the advantage of being much more affordable. It is also worth noting that manufacturers are beginning to tackle the screen door and contrast issues and newer models are able to offer improved image quality. For these reasons it is hardly surprising that many manufacturers continue to use the technology in devices through the low and high ends of their product ranges.

DLP technology was introduced in the late nineties by chip manufacturer Texas Instruments and since then it has had a major impact on the projector industry and continues to play a key role in the development of the market. DLP technology is exclusively licensed by Texas Instruments which sells DLP chips to the projector manufacturers who then build their machines around that basic building block. The workings of the technology are complex and a little more difficult to understand than LCD. In short, a light source is shone through a colour filter which alternately (but faster than the human eye can distinguish) shines red, green and blue light onto a DLP chip. The DLP chip contains thousands of tiny computer controlled mirrors and these reflect the light very precisely through the projector lens to make up the complete picture.

The current obstacle faced by DLP technology is that it is not able to produce brightness levels as high as LCD technology, and in situations where you might not be able to get complete darkness (such as board rooms with large windows) this can make it difficult to see the projected image. However, DLP technology offers excellent contrast ratios and far better moving image quality than LCD. Another key advantage of DLP technology is that it is considerably more compact than LCD which allows manufacturers to produce tiny, lightweight projectors that are capable of delivering great image quality. Although portable LCD projectors have been around for a while, it is only with the advent of DLP technology that the mobile projector market has really taken off. Their portability and good video quality makes DLP projectors a favourite with business users who also want to take the device home at weekends to play DVDs on the living room wall. This trend has not gone unnoticed by the manufacturers and many features found in home-cinema projectors (such as side-throw) have begun to creep into the business projector line-up.

Generally speaking DLP projectors are based on a single DLP chip – but at the high end you may find machines that use three separate chips, one for each colour. By using three chips these devices are able to offer higher lumen levels than both single chip DLP and LCD projectors. These machines offer just about the best image quality it is possible to obtain from a digital data projector, but this is reflected in their considerably higher price tag. Clearly the additional processors and associated optics mean that such machines are also likely to be bulkier and far less portable than other DLP devices.

The newest technology to enter the digital projector arena is called LCOS (liquid crystal on silicon), which is usually described as being an amalgamation of DLP and LCD technology. The key advantage of LCOS is that it allows for higher image resolution that the other technologies and even the base models start at 1365×1024 pixels (although you may find one or two slightly lower resolution models). There are several inherent design advantages which allow LCOS to deliver considerably better image quality than LCD and single chip DLP processors. The main issue with such machines is that as with all cutting edge technology the manufacturers have yet to ramp up production to the levels where economy of scale savings can be passed onto buyers, so they are still very expensive.

Buying Advice

All of the manufacturers agree that the key to making a good buying decision is to be absolutely clear about what you want to use the projector for and what kind environment you will be using it in. Once these factors are clearly defined you can set about finding a machine that best meets your requirements within your allotted budget. “Be clear about what you actually need, it’s easy to suddenly find you have got a projector with lots of things you do not actually require. So think about the kind of environments you are going to be presenting in. Do you have much control over the light? If you do not then perhaps you go for a higher brightness projector. Ease of use is key, all of our models have features designed to make them easy to use – you do not want to be messing around with settings while you are out in front of a customer.”

 

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