Lamp life. Projector lamps can be replaced by the user and all the products include removal and replacement instructions. Lamp life ranges from 2000-3000 hours depending on the setting you use. If you're watching a lot of TV or playing video games, it could work out to be pretty expensive; lamps typically cost about $450-660 to replace. That's anywhere from about 15-33 cents per hour of viewing. All the projectors count the hours of lamp operation and separate the lamp warranty into a period of time (three months, for example) or hours, whichever comes first.
Boot time. The projector lamp needs time to heat up before it can display a picture. For the sake of the life of the lamp, it's a good idea to let your projector heat up and cool down according to manufacturer instructions.
Noise. Just as people whispering in the row in front can ruin a night at the movies, so too can a noisy projector fan. The sound produced by the projector will vary depending on whether it's in high brightness or economical mode. The claimed sound levels of the projectors range from 26-33 decibels.
Heat output. After an hour playing footage from a DVD on its default settings, the temperature of the projectors ranged from 53°C (Epson) to 82°C (Optoma). That's toasty, so keep small children and clutter away from the exhaust outlet. The projector should also be used in a well ventilated room, or else things could become uncomfortable.
The physical size of the projector doesn't necessarily have any impact on the resolution it can display. Three of the projectors have a native resolution of 1280 x 720, which you may see listed as 720p. They're considered high definition (HD) projectors. All products use progressive scanning, but the resolution of the Sharp and InFocus projectors, 480p, isn't a high definition standard. Both projectors performed better than the Epson and BenQ, however, because they could produce good colours, although the Infocus lacked some detail.
The native resolution is the resolution at which the projector can display images without having to scale the picture up or down. The ideal situation is when the video signal matches the native resolution, but in reality you'll be watching video from different sources at different resolutions.
If you're after the highest native resolution possible, you'll now find projectors with native resolutions of 1080, often referred to by manufacturers as True HD or Full HD. They're still very costly - more than double the most expensive projector in this test.
The keystone effect usually occurs when the image is projected to the screen at an angle. If projected upwards, it results in picture that is wider at the top and looks like a wedge or 'keystone'. All the projectors had controls to overcome this problem. The InFocus lets you correct the vertical image by up to 20° and the Optoma is the only product that lets you correct the image both vertically and horizontally.
Keystone correction can create jagged edges at the edge of screen, since it effectively cuts out some of the pixels to make the image rectangle.
You can adjust the colour of the projected image using the basic colour correction functions of the on-screen display. The BenQ and Epson also include a handy shortcut on the remote control.
You can also adjust individual colours (red, blue and green) but these functions, called gain settings, can be hard to access.