Lab

Home cinema projectors

Whether you want to give a PowerPoint presentation to a room full of people or watch movies in a cinema-like setting, a projector is the only way to go. Even the cheapest projector here can project a huge 58in image at seven feet.

In this month's Labs we've got 12 projectors: eight for the office and four home cinema devices. The office projectors tend to be smaller and lighter, and are designed for use with a PC for presentations. The home cinema projectors are geared up to deliver HD content in widescreen aspect ratios.

If you need a projector that can cope with both jobs, you won't be disappointed. Here you'll find office projectors with HDCP-compliant inputs for HD movies, and home cinema projectors with PC inputs that can control a slideshow. The best thing is that all the projectors here cost less than £1,000, and some are half that. Whatever you need, we'll help you get the biggest and best display for your budget.

There are two categories of projector, office and home cinema, but the line between the two is blurring. Many office models are perfect for watching movies, and home cinema models are often capable of controlling presentations and taking a PC input. This can make choosing the right projector difficult, so before you start looking, you need to decide whether you want a projector for one specific task, or a flexible projector that you can use both at home and at work. If flexibility is what you're after, you need to consider which job your projector will do most.

DLP and LCD

There are two types of projector technology: liquid crystal display (LCD) and digital light processing (DLP). LCD projectors work by splitting the light source into red, green and blue components. Each frequency of light passes through a small LCD screen. The images from all three displays are combined and pass through a lens to create a colour image.

DLP projectors use a single digital micromirror device (DMD) chip, which is made up of thousands of tiny mirrors, one for each pixel on the screen. The chip controls the angle of each mirror to turn it on, in which case it reflects light through the lens and the pixel is white, or off, in which case light is reflected away from the lens and the pixel is black. By turning the mirrors on and off very quickly, the DMD can create shades of grey. To produce a colour image, a spinning colour filter called the colour wheel is placed between the light source and the DMD. In older models this has three segments, allowing red, green and blue light to fall on the DMD. By synchronising the DMD's mirror movements with the colour wheel, three different images are projected for each frame. Our eyes then combine the red, green and blue images into a single image with the correct colours (see www.dlp.com for more information).

The main problem with this system is that fast-moving objects in movies, for example, can put the three frames slightly out of sync, creating a burst of rainbow colour known as the rainbow effect. Some manufacturers have reduced this by adding more colour segments to the colour wheel. Our reviews will tell you where this is a problem.

DLP's main advantage is that the small chip enables manufacturers to produce tiny portable projectors, which are perfect for business. As LCD projectors have to accommodate three small screens inside, there's a physical limit to how small they can be.

DLP's other advantage is that pixels can be turned on or off completely, so projectors that use this technology have high contrast ratios, which means they produce dark blacks and bright whites. LCD technology produces lower contrast ratios, so blacks can look grey and whites dim. However, home cinema projectors use dynamic irises that constantly adjust the amount of light projected on the screen. This creates high dynamic contrasts for dark blacks and bright whites. LCD projectors generally produce better colours than DLP and have a sharper picture. With no rainbow effect, they generally produce smoother and better-looking video.

Brightness

A projector's ANSI lumens rating tells you how bright it is. The higher the ANSI lumens number, the brighter the projector will be. For business use, the projected image must be bright enough to show an image clearly under standard office lighting. As a rough guide, 1,200 lumens is good enough for a dimly lit room, 2,000 lumens is fine for standard office lighting and 3,000 lumens or more is required for use under very bright light. Home cinema models will almost certainly be used in a darkened room and so are not as bright. However, all four home cinema projectors in this test have a rating higher than 1,000, and one is as high as 1,600 ANSI lumens.

Movies and presentations

An office projector will spend most of its life displaying computer applications, such as PowerPoint. For this purpose the ideal aspect ratio is 4:3, which is the ratio of all the office projectors here. Look for a projector with a USB port, as this enables you to control your presentation with the remote control.

Home cinema projectors have widescreen aspect ratios (generally 16:9), so they're close to the ratios used by films and television. All the projectors in this group are HD ready, so they're HDCP-compliant for Blu-ray and HD-DVD players, and have either HDMI or DVI inputs, as well as a component input.

If you're looking for a projector to use both at work and at home, our reviews and table tell you which office projectors can play HD movies and are HDCP-compatible, and which home projectors can be hooked up to a PC and control presentations. Our table also tells you which other inputs the projectors have, so you can see whether you can connect your DVD player, games console or other equipment.