Projector Display Types: CRT or DLP or LCD?
CRT or DLP or LCD Projectors?
This is where most of the confusion lies – everyone has a favorite. I won’t tell you what is “better”. It’s a personal choice, based on many subjective factors. What I will tell you is that, in my experience, while DLP may well be the outright better technology for all applications, that day is still in the future. There are some very interesting developments on the way from the LCD guys, so keep your eyes peeled.
Cathode ray tubes. This typically involves a blue, a green, and a red tube. Extremely high maintenance is required (unlike projectors that use lamps). Maintenance costs are very high in price. You are better off in buying a middle of the line DLP or LCD projector for the cost of maintenance, although it is seen most often in very expensive (over $10,000) fixed systems.
Liquid Crystal Display. A current is passed through a crystallized organic compound, changing its shape on a molecular level. Zap them, and the crystal molecules change their shape, allowing red, green, or blue light to pass. On moderate to mid-range priced projectors, you get better bang for the buck from LCD. LCD colours tend to jump out at you more, and tend to be richer and more vibrant. Because there has to be a physical separation between pixels, LCD projectors can suffer from a “screen-door” effect. It’s referred to as this because it can be like looking out a screen door; everything is divided into little squares separated by a thin black line. The screen-door effect of modern LCD projectors has been minimized – the pixels are much closer together than previous versions.
Eventually, all that molecular shape changing takes its toll – the crystals begin to react slowly, or may even break. This means that eventually, your LCD projector will age, the liquid crystal becoming so unresponsive that the panels become useless. The organic compounds the liquid crystals are made from will also eventually discolour and burn with exposure to bright light, turning yellow with time. While this is a fact of life, it takes an incredibly long time to achieve, years of operation, so shouldn’t really concern you.
Digital Light Processing. White light is shone through a spinning colour wheel (red, green and blue). The coloured light is bounced off a panel made of millions of micro mirrors, then from the mirrors through a lens assembly. The chief advantage of DLP is texture. Because of how it works, there literally is no space between pixels on a DLP projector, and as a result, no screen-door. Colour has been improving as well, and on more expensive DLP projectors, colour accuracy and intensity surpass even the best LCD projectors. The chief liability of DLP is the spinning colour wheel. Less expensive DLP units spin the colour wheel at a lower speed (2x) than more expensive chips (4x and above). This can result in a disconcerting colour oscillation (aka “The Rainbow Effect”) that is very uncomfortable for some people. Again, the effect is minimal on higher end, faster spinning, DLP chips.
DLP colour wheels are often segmented. This improves the performance of the chip by increasing the effective speed the wheel spins at, thusly increasing the speed at which the colours are refreshed. We recommend avoiding 2x or 2 segment colour wheels particularly, as these tend to be most prone to the Rainbow Effect. These chips tend to be found in entry-level DLP projectors. Opting for a 4x or better, while costing more money, significantly reduces the possibility that your movie or presentation will give your audience a headache.
So there’s no clear winner in CRT vs. DLP vs. LCD – they both have significant strengths and weaknesses. A good rule of thumb? CRT devices are suitable only for fixed installations, LCD for low to mid-range units, and DLP for higher end installations.