1 Projection and imaging systems
1.5 Projection area (screen)

The correct placement, the position of the projection plane, in relation to viewers, is conceptually based on several of the following recommendations:

1. Image height - conceptually based on the dimension of the distance x to the most distant spectator

- for an overview –
- for reading –
- for details –

2. Distance to the nearest spectator

- Infocomm - distance = 1 × image width
- Projecta - distance = 1.5 × image height

3. Bottom edge of the projection screen from the floor – at least 110 cm

Basic distribution of projection screens:

- Front Projection - The projector is on the same side as viewers
- Rear projection - The projector is on the opposite side to the viewer

It is also possible to classify projection screens according to the design: with a roller shutter (operated manually or electrically), with the frame-to-wall, with mobile frame, with tripod and with the cinema screen.

The format of the screen is specified by two dimensions - width and height (W × H). Taking these two dimensions into consideration, the projection surfaces can be divided into:

- universal - 1:1
- widescreen - 16:9 or 16:10
- conventional - 4: 3 (now less used)
- cinema - 2.35:1

Why is the widescreen format now preferred?

There are two reasons. The first one is that the maximum screen size is often limited by the height of the room, the second one is that at the same height of the screen as compared to the conventional screen more information is displayed.

Each screen has its own specific surface, which we choose with regard to the type of projection:

- Diffusion surface for front projection - reflects image in all directions in the same way (parameter gain = 1.0 - 1.1, viewing angle 100° - 120°)
- Diffuse surface for rear projection - directs the image in all directions equally (gain = 0.9 - 1.3, viewing angle 60° - 130°)
- Progressive HD Surface for Front Projection - specially designed for Full HD, 4K or higher, reflects the picture in all directions in the same way (gain = 0.6 or 0.9 or 1.1 or 1.3, viewing angle 150° - 170°)
- Optical front projection - reflects the image in all directions equally (gain = 0.8 or 2.3, viewing angle 46° or 170°)