Projection film is an updated 2011 technology on the standard type of movie projector process that uses a polymer-based film that is adhered to an acrylic or glass sheet surface. The film has microscopic materials embedded within it that give it the ability to respond in unique ways to a light image projected on it from a video projector mounted behind it. The film displays optics properties such as reflection and diffusion of light that make the acrylic or glass surface both a visual display and an interactive medium. The surface can serve as a touchscreen that responds to viewer commands or a point-of-sale marketing system for products. One of the main advantages that such film offers is that, when the video projector is turned off, the glass or acrylic screen to which the film is attached can become an ordinary window that is part of a retail establishment.
Rear projection film (RPF) is available in rolled sheets that are self-adhesive and can easily be cut to custom sizes and adhered to a glass or acrylic surface. It is designed to allow for the viewing of images from any angle, and can be easily removed from the surface or integrated with other built-in graphics that are already on the glass. A touchscreen type of film is often applied underneath the RPF itself to give the visual display interactivity. Large projection surfaces use the film for applications such as trade show displays or digital signs in retail stores and organizations such as museums, where smaller versions are used to create interactivity in kiosks and for individual touchscreens.
Projection surfaces tend to be less important in the quality of images produced by projection film than the video projector itself. While the film is versatile and will work with most any video projector to create front projection film results or standard results from behind the surface, the higher the quality of the projector, the better the image that will be displayed by the film. Rear projection is often chosen over forward projection as it allows for the video projector to be concealed and eliminates shadows that are created if objects pass between a forward projector and the film.
Often the deciding factor on quality for the results of an image produced by projection film glass surfaces is the amount of light or lumens that are being directed at the square area of film from the video projector. An 80 inch (2.03 meter) on one side screen will display a much more vivid image if the screen is located in an interior building away from outside light than an image with the same amount of lumens and size that makes up an exterior glass wall of a retail store. The type of lighting used by the projector also makes a difference, with standard incandescent light bulbs casting less lumens on the screen than light emitting diode (LED) sources.
The larger a projection film surface is, the farther away that a video projector has to be from it to cast a clear image on the film. This is known as the “throw ratio” or “throw distance” for the projector and is a multiple of the width of the screen. Other determining factors in the quality of a projection film image can include the sophistication of the film itself, as some materials are based on liquid crystal display (LCD) technology that generate their own colors, contrast foils that display darker images, or standard white film that relies mostly on the quality of the video projector for satisfactory results. Some types of projection film are also designed to simply display an opaque gray image when switched off and become transparent when on as a form of convenient privacy barrier in offices and homes.