Projector screen is a surface used for projecting images that also usually comes with a supporting structure. The projections are either front projection or rear projection type, with the former being more common. Depending on various other factors, the projectors are also categorized into fixed, portable, electric, and manual. The manual screens are very easy to roll in and out and are also quite affordable, while the electric screen are slightly costlier, but also roll out and retract easily. The fixed screens are typically mounted on a wall and suitable for dedicated home theater rooms, while the portable projection screens are great for presentations, traveling trainers and other people on the go since they are very easy to set up.
The most common projection are either white or gray with the gray ones designed to boost contrast and capable of better absorbing direct ambient light. However, choosing between the two depends on various factors like the type and contrast of the projector and the amount of light in the room itself.
Another type of projections are the switchable projection screens – they can be switched between clear and opaque and allow you to easily turn a window to a screen where images can be viewed from both sides and from different angles.
One very important characteristic of the projections is their gain – this is the reflection factor of the screen and typically ranges from 0.8 to 2.5 or more. Higher screen gain does not necessitously mean better viewing experience since they can have hot spots where the center of the screen is brighter than the sides of the screen, but this is less of a problem with high gain screens that are retro-reflective or curved . When curved projection screen is positioned properly and aligned correctly to the seats, then the whole screen becomes a "hot spot" and the picture brightness is uniform.
The screen geometry is another important factor and refers to the aspect ratio of the screen (the width divided by the height). The most common aspect ratios are 4: 3, 16: 9, and 1: 1. The 1: 1 screens are obviously square and typically used with overhead projectors, but can also be suitable for places with limited space. The 16: 9 screens should be used with HDTV Video projectors and 4: 3 with NTSC Video and Pal Video.