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Audio Visual Support

As a result of the workshop on Multimedia Lecture Room Services held earlier this year, AGOCG are providing a new service to support Audio Visual services. A new web site will provide details of, and links to, national support services and local media services around the country, such as colour printing, video production and scanning and digitising services. In addition the site will contain briefing papers on AV and multimedia related topics and information regarding multimedia standards. Current briefing papers include Providing Multimedia Lecture Room Services and Choosing an LCD Projector.

If any media support or AV support departments in Higher Education institutions would like to advertise their facilities on this site, please contact Sue Cunningham (

Choosing an LCD Projector

One of the main concerns in delivering multimedia presentations has always been unreliable or unsuitable projection equipment. Fortunately LCD technology has advanced significantly from the first dim VGA LCD panels and good quality, high resolution, projectors are now available. There are however, a number of important points you need to consider when choosing new equipment.

Image Size

Image size depends not only on the projector, but also on its positioning in the room, the further away, the bigger the image. It is very important when making a comparison to ensure all the models are the same distance from the screen, and that it is a similar distance to a real use situation.


Many projectors today offer 800x600 resolution as standard. They differ, however, in how they cope with other resolutions. At lower resolutions (640x480), some are able to resize the image to fill the whole screen. To achieve a high quality image, however, resizing may not be desirable, so look for an optional, rather than auto-resize feature. At higher resolutions, some method of compression is employed. This means that data is lost, and the image quality will therefore decrease. Compression methods vary however, and it is worth checking the quality with typical screens if you plan to use this feature.

Colour and Contrast

To a certain extent, determining which projector provides better colour is a subjective exercise, and will depend on the exact contrast and brightness settings. However, it is worth displaying the same images through different projectors to compare. Test images should include some with a wide variation in shades, and some with large areas of solid colour.


Where to site a projector is a very important issue. It must be at a reasonable distance to give a good quality image with a reasonable size, but must not interfere with the view of any of the audience. Many projectors support three methods of mounting:

Front - the standard viewing position. The main disadvantages are that the projector may obstruct the audience's view, or that the presenter may block the image path.

Rear - this requires a special projection screen, and a similar amount of room behind the screen as would be required for front projection. It is usually only found in very large lecture theatres.

Ceiling - perhaps the best solution as the projector is not in line of sight, and is less likely to be accidentally damaged or stolen. As the projector will usually be mounted upside down, it must be possible to invert the image. In addition to the cost of the mounting, a cable booster may also be required if the projector is more than a few meters from the computer.


Keystoning occurs when the projected image is not square, e.g. the top of the image is larger than the bottom. This is caused when the projected image is not perpendicular to the screen, and so can be corrected to some extent by tilting the screen. Most projectors have some degree of keystone correction built in, allowing the projector to be placed off centre. As the degree of keystoning is dependent on the position of the projector, it will be different if the projector is front or ceiling mounted. While a few projectors allow the degree of keystone correction to be altered, most have a fixed correction.


Multiple inputs may be useful in a conference situation, where speakers are using different computers, allowing all the equipment to be setup before the session.


Remote controls are included with most projectors, and may act as a remote mouse. This is a useful feature, as the presenter is no longer tied to the computer. Most remote control units are infrared, with sensors mounted on the front of the projector capable of receiving commands bounced off the projection screen. To prevent frustration later, it is important to check the projector comes with a full set of cables, including those for connecting to PC and Macs and where appropriate video and audio cables.

For more details about the technology behind LCD projectors see:

Sue Cunningham
Manchester Visualization Centre
Manchester Computing
University of Manchester
Manchester, M13 9PL

Tel: +44 (0)161 275 6095
Fax: +44 (0)161 275 6040