There are plenty of so-called portable projectors weighing in at three or four hernia-inducing kilos, which is to say they're probably heavier than the laptops that drive them. To our minds a truly portable projector should tip the scales at around 2kg, and to be classified as an ultra-portable we'd expect a projector to weigh less than 1.5kg and have a commensurately small footprint.

The BenQ CP120c certainly fits the bill at 1.3kg, and is the size and shape of a typical software box. Its small size does not compromise its performance, and even though its output is only 1500 lumens, this is easily bright enough to be used in an office or conference room without dimming the lights, provided there's no sunlight streaming in through the windows, of course.

The projector will appeal to two obvious groups of users: mobile professional presenters armed with PowerPoint slideshows and home entertainment buffs who don't have the space for a permanent home-cinema installation. A cash-strapped student living in a bed sitter could enjoy DVD movies by projecting them onto a blank wall and listening through headphones, while for the peripatetic presenter in a formal venue there's the possibility of filling a 6m x 4m screen from a projection distance of 11m. At the other end of the throw range, the smallest possible image is just under a metre wide, which requires the projector lens to be no closer than 1.75m to the screen.

As with all projectors, there's an optical zoom control, but this doesn't work like the phenomenal zooming capabilities of a digital still or movie camera; it's really just to fine-tune the image to fill the screen without having to move the projector back and forth.

An ultra-portable projector needs to be able to withstand the rigours of the road, and the BenQ excels in this respect. It is sturdily constructed of plastic and metal with an impossible-to-lose sliding lens cover and a damped, spring-loaded front support that makes its rivals' wobbly legs look pathetic.

Like most projectors based on Texas Instruments' DLP chip, the BenQ runs cooler than similar LCD devices and displays much higher contrast, and if you're using it to make public presentations and just can't wait to get away afterwards, it has an optional fast-cooling mode that enables you to pop the machine into its well-padded case and make a quick getaway within 30 seconds of finishing your spiel.

Ergonomic features we liked include a credit-card-sized remote with logically laid-out buttons, a control panel that glows in the dark and a zoom ring with a lever to distinguish it from the focussing ring; useful when working in dimmed lighting. The fan vents air through the front of the projector and the back is completely light-tight, so audience members sitting behind the projector are not distracted by stray light or in danger of scorched eyebrows.

The projector auto-senses the input source, which can be from the VGA slave socket of a laptop or the S-Video / composite video output of a DVD/TV recording device, and the keystone distortion that makes a supposedly rectangular screen look like a trapezium is also corrected automatically, so all the user needs do apart from connecting the cables correctly is focus the lens.

The menu system is less complex than most, and therefore easier to use, but it lacks refinements such as manual Gamma setting and the individual manipulation of red, green and blue channels. Another slight drawback is the lack of audio output, but as most projectors offer little more than a 1W speaker, anybody thinking of using any sort of projector for movies and audio-assisted presentations will want to add an amplified audio system anyway.

It's not the cheapest lightweight projector, nor the brightest, nor the most sophisticated, but in terms of build quality, portability, ease of use and image quality it's hard to beat. If BenQ could get the price down to £500 including the taxman's cut it would blow away its rivals.