Total Visual Solutions - Screens

Screens

Screens are available in many different configurations for use with video projectors and OverHead Projectors (OHP).

The first consideration is the size of the screen required. Screens are available from 4' to 17' diagonal picture size in standard sizes; screen sizes are still commonly quoted in imperial. Larger sized srceens often seem a good idea as a large picture can be seen by more people. However it is worth noting that the larger the size of the screen, the greater the image brightness is distributed across it. In other words if the size of screen in doubled then the perceived brightness is halved. Although it does depend on the specific ambient ligh in any room it is a rough guide that a 2000 ANSI Lumen projector will comfortably fill an 8'x6' screen in most conditions.

With regard to size it is also worth noting that an OHP will normally provide a square image whereas a video projector will provide a rectangular image with a 4:3 ratio. Therefore it goes without saying that an OHP will look and fit better on a square screen and a video projector will best fill a 4:3 screen (ie 8'x6' or 12'x9').

If the trade off between size and brighness causes problem or if the projector needs to be out of sight then it is worth considering a rear projection screen. Unlike standard screens which are made of black-backed highly reflective material, rear projection screens are semi-opaque. The idea behind this is that the light shines through the material rather than onto it. With standard screens the light from the projector shines onto the screen and is then bounced back to your eyes meaning that some light is absorbed by the material and in the extra distance of travel. With rear projection the light shines directly into your eyes (through the screen material) therefore increasing the perceived brightness of the image. The only downside to this option is the viewing angle. Because the light is shining through and not bouncing off the screen the angle of viewing can be reduced by as much as 30 degrees each side of the screen. The only other thing to note with this option is that as much space is needed between the projector and the screen fro both front and rear projection. Therefore a minimum of about 5' is required behind the screen and if this is not possible then this option is not reasonably viable.

The more conventional options for screens are the floor standing (tripod) and wall mounted versions. With both of these types they can only be used for front projection (for obvious reasons). The main difference between the two is that the tripod screen is very portable if required and can be used where a wall is not available or if the screen needs to be removed.

An upmarket alternative to the humble wall screen is an electric screen. Much as the name suggests these have a built-in electric motor which is used for raising and lowering the material from a fixed box. This is particularly useful if the screen is not in use all the time and needs to be hidden from view.

For applications where the screen needs to be moved to different locations or it is not suitable to have a fixed screen then there are three alternatives. The first is the standard tripod screen. With the material unrolling from it's box and simply hooking onto the stand this is a quick and easy option. The downsides to the portability are that screen sizes are limited to around 6' so that the tripod assembly does not tip over. Also it is hard to obtain good tension across the screen when it is only supported in the middle at the top and bottom. Invariably the material box will twist slightly giving high tension to one side and wrinkles to the other.

The best compromise between quality and portability is a Fast Fold screen. This is made up of two main parts: an aluminium framework and the seperate material. The framework is unfolded and snapped together to make a very strong and lightweight surround. The material is tensioned over the frame and fastened using poppers. Assembled in less than 5 minutes these screens can exceed 15' diagonal if required but are also available in standard sizes. The rectangular frame ensures that screen tension is perfect but also means that it can be used for front and rear projection just by changing the fabric. This is ideal for those who may want to use both as only the spare fabric needs to be purchased as opposed to a whole new screen thus saving costs.

The ultimate in portable screens has to be the Harrier. The name comes from the Harrier Jump Jet, an aircraft capable of taking off and landing vertically. The principle behind the harrier screen is very similar. The whole screen is supplied in its own wooden protective case which forms the base when it is erected. Once opened you grab hold of the screen handle, lift up and let go. The scissor mechanism behind the screen ensures it stays up at many heights without the need for additional supports making it one of the quickest screens to put up and take down (to put down, all you do is push).