Bigger is better in display technology, right? If that's true, surely a projector painting a life-sized spectacle across your living room wall is going to be hard to beat?

The reality, of course, is much more complicated. On the one hand, projectors are capable of truly cinematic images, the likes of which no monitor or HDTV can possibly conceive.

That's an especially intriguing proposition when you consider that a decent enough projector with HD visuals can be had for as little as £400. It's also worth remembering that LCD panel technology of the sort that dominates PC monitors and HDTVs is not terribly suitable for multimedia viewing.

Things like viewing angles and contrast are problems that are unlikely to be properly solved before LCD panel tech is replaced by full LED displays (as opposed to LCD screens with LED backlights).

The other side of the coin involves practicality. Something like a large but conventional LCD monitor can turn its hand to most tasks you throw at it. Most monitors are great for soaking up web content or getting work done. They're usually pretty nice for playing games, too. Movies don't look bad, either.

More to the point, you can use them at any time of day in more or less any kind of room. Not so for projectors.

For starters, even powerful projectors look pants in daylight. Yes, you can get models with lamps bright enough to blow a hole in your living room wall, but it still won't look as vibrant as a monitor or HDTV. Projectors, for better or worse, are mostly nocturnal beasts. Even if lighting wasn't an issue, using a projector to do desktop work or browse the web would be ludicrous.

In that sense, projectors fall into the as-well-as rather than instead-of category. But here's the thing: when they're good, they're spectacular. Movies and games are taken to another level. And while we're not entirely won over by stereoscopic 3D tech, it works best playing games on a projector.

They cost less than you think

Now that we've won you over to the proposition of a projector, let's kick off with some good news. You can bag a decent beamer for as little as £400. Yes, we're talking HD and DLP, though as we'll see, the latter isn't compulsory for decent big screen giggles.

That matters because a projector isn't likely to usurp any of the screens you already have. It's a desirable extra, but an all-purpose, do-anything display a projector most certainly ain't. Of course, like most things, spend more and you'll get more.

The most obvious trade-offs involve resolution and support for 3D technology. We'll get into the details in a moment, but the question regarding resolution is whether you're happy with 720p for what is inherently a display technology optimised for very large images, or whether you're willing to stretch for full 1080p visuals.

As for 3D technology, it's largely a question of support for 120Hz refresh rates. That adds a certain amount of cost and complexity to the projector itself, but also has implications for your PC. Like we said, we'll come back to that.

First, let's wind back a little and have a look at projector basics. The classic contest is between DLP and LCD technology. Strictly speaking, there's a third option: LCoS or Liquid Crystal on Silicon. But ever since Intel bailed out on LCoS back in 2004, the odds of it becoming mainstream have looked slim.

For the future, LED looks like it might become a contender for full-sized projectors. It's also more of a light source technology than image source and currently restricted to compact, portable units.

Now, it used to be the case that the choice for gamers and movie buffs was simple: you wanted DLP, but were you prepared to pay for it?

Part of the reason for that involves the fact that DLP, or Digital Light Processing, is something patented by Texas Instruments. With a monopoly on DLP, TI has tended to charge a premium. At the same time, DLP has had a number of critical advantages over LCD in terms of image quality.

To understand why, it's worth recapping the basics of both DLP and LCD in projectors.

Beamer basics

As it's the easier to get to grips with, we'll start with LCD.

The basic principles are nearly identical to LCD monitors and TVs. Knock up an LCD panel with a grid of pixels. Shine a light through the back and turn the pixels on and off by manipulating the liquid crystals in each pixel to either block or allow light to pass through.

There are differences, of course. With a projector, the backlight is a lamp and much more powerful than what's found in monitors. And you're not directly viewing the LCD panel. Instead, the light is harnessed via optics, including lenses, prisms, polarisers and mirrors and thrown out onto a viewing surface.

Another major difference between LCD projectors and LCD monitors is colour production. For monitor panels, each pixel has three primary-coloured sub-pixel. Not so for LCD projectors, instead they have three individual panels, one for each primary colour. White light from the lamp is split using dichroic mirrors, sent through the three panels and then recombined with a prism.

As for DLP technology, you could say it's the polar opposite of LCD. Instead of relying on light transmission through a panel, DLP is all about reflection. The really clever bit is known as the digital micro-mirror device.

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This is essentially a chip with a grid composed of thousands, or even millions (in a full HD projector), of tiny mirrors arranged in a grid. Light from a powerful lamp is directed onto the chip and each mirror can be angled individually to either reflect light into the optics, which is effectively the 'on' state for each pixel, or dump it onto a heat sink.

While some really high-end projectors have multiple chips to create colours, the sort of projectors we're dealing with tend to use colour wheels. The idea here is to shine light through a series of coloured filters, switching the mirrors for each colour. Do the process fast enough and the human eye resolves the cycling images into a single, full colour image.

If that's the basics, what are the pros and cons of LCD and DLP? In the LCD ledger we'll put colour accuracy and pixel definition. The pixels in an LCD projector are essentially perfectly defined, whereas DLP pixels have slightly soft edges. For projecting data, that gives LCD a clear advantage.

However, for games and movies you could argue that a soft edge to pixels gives a smoother, more natural image. What's more, DLP pixels tend to be more tightly spaced. Put the two together and the result is that the pixel grid tends to be less visible with DLP than LCD. Win, in other words.

As for colour accuracy, part of the problem for DLP is that colour wheel. It makes resolving colours accurately more difficult. However, while the colours from LCD panels are strictly speaking more accurate, DLP colours tend to look more natural and vibrant. Again, the balance tilts in favour of DLP.

While we're talking colour wheels, one other very clear disadvantage of DLP is the so-called 'rainbow effect' suffered by single-chip models. In theory, the colour wheel spins fast enough that the entire is invisible.

In practice, some cheaper projectors have wheel speeds and colour segment counts low enough to create a problem for a small subset of particularly sensitive users. What they see is hard to describe, but in simple terms involves a separation of colours, particularly when the viewer moves his eyes across the screen. Whether you'll be one of those sensitive types is tricky to predict. But avoiding the very cheapest models is advisable if you want to be absolutely sure.

As for DLP, its killer advantage has traditionally been contrast. Again, this comes down to the transmission-versus-reflection divide. An LCD panel capable of blocking all or very nearly all light has yet to be devised.

For DLP, generating a truly black pixel is much more straightforward, with the mirror effortlessly diverting light away from the optics. Of course, there's always a little background noise in the optical system. But DLP projectors come very close to delivering truly black pixels. When it comes to cooking up really cinematic visuals that counts for a lot.

Having said all that, as competing technologies improve, they also tend to converge. Scope out the latest 1080p LCD units, for instance, and you'll find the pixel grid is borderline invisible. LCD as a technology for home cinema has come a long way, too, which helps to keep Texas Instruments and its DLP technology honest.

Picking features

3D

To find out more about the comparison between DLP and LCD, check out the individual projector reviews overleaf.

But what else do you need to know? Well, first up is the question of resolution. In isolation, the answer is simple. Go for 1080p. The rough starting price for a full HD projector is £700 and while that's a hefty premium, it's worth the extra.

Partly, that's because the whole point of projectors is to paint a big picture. But it's also because 1080p is likely to be the standard for HD visuals for many years to come. In other words, unlike most technologies which are in constant peril of being outmoded or usurped, 1080p has legs. Buy a full HD projector today and you won't be coveting something clearly superior almost overnight.

However, if you add stereoscopic 3D into the mix, it's not so simple. There are a couple of reasons for that: in simple terms, 3D adds yet another premium, so 1080p plus 3D can get pricey. You've got to draw the line somewhere.

The other problem involves system performance and compatibility. Today's 3D projectors rely on active-shutter technology. As with any 3D technology, each eye gets its own view with a unique - if only slightly - perspective. With active shutter technology, the images are alternated rather than overlaid. That creates a need for double the frame rate compared to conventional projectors; typically 120Hz for a 3D projector compared with 60Hz for a normal model. And that, in turn, can create a number of problems.

First, the video interface needs double the bandwidth. Most recent PC video cards support HDMI 1.3, which is the interface of choice for 3D. But not all do. You'll also need quite a powerful video card, since you're doubling up on the rendering load, too. At 720p, that's not a major issue. But rendering two 1080p games in high detail? That's a significant ask if we're talking the latest, greatest games.

Then again, if you're considering getting a 3D projector for games, you've probably got a decent budget to play with.

Doubling up on the image also has implications for quality. For starters, running projectors in 3D mode makes for a duller image. With a DLP projector, that's partly because you need even more wheel segments and rotation of colours. But for any projector type, each eye is effectively only being lit up for half the time.

All of this, of course, assumes you buy into stereoscopic 3D in the first place. We're not convinced 3D tech has truly come of age. Whether it's silly glasses, reduced image quality or the discomfort that comes with viewing 3D stuff for hours on end, it doesn't seem quite right yet.

That said, if there's an activity that lends itself best to stereoscopic 3D, it's got to be games. 3D cinema is a gimmick and 3D video on an HDTV, likewise. 3D games on a projector, we have to admit can be pretty spectacular.

As for other general rules of projector purchasing, we'd say think LCD monitor. By that we mean many of the same caveats apply. Just like LCD panels, you should take quoted specifications with a proverbial pinch. The classic example for LCD screens is contrast ratios and that applies to projectors, too.

The big problem is manufacturers quoting dynamic numbers. That involves varying the light source intensity and it's just no substitute for good, native contrast. Unfortunately, some manufacturers don't quote native contrast and for that reason, it's hard to put a figure on the minimum you should be looking for. Where it is quoted, 1,000:1 and better is acceptable.

As for brightness, don't be fooled into thinking brighter must be better. Yes, a stronger lamp makes for better viewing during the day and a powerful lamp of 2,000 lumens or more makes for a flexible beamer. But all projectors look best at night and 1,000 lumens is plenty in that context.

We'd also warn against using keystone correction if at all possible. The idea here is to digitally tweak the image so that the projector needn't be mounted perfectly central. However, there's no avoiding image degradation when correcting the image this way.

One handy way to sidestep the problem is to use a ceiling mount of some kind, which keeps the projector from cluttering up your living rooms. It's also great for keeping the projector out of harm's way if you have kids or pets tearing up the floor space.

In short then, lets forget the neighbours and their silly little flat screens, and let's break out the beamers.