Reflectance (gain):
Reflectance is measured as "gain". Gain refers to a fixed reference standard – magnesium carbonate (MgCO3) absorbs no light but reflects the projected light back perfectly evenly.
The typical fabric types are:
Type D (d = diffuse)
Type D screens reflect the projected light evenly in all directions and have a matte white surface. This type allows good viewing angles of up to 60° to the right and left. The gain is 1.0 – 1.2, making it ideal for projection in living rooms and conference rooms.
Type S (s = specular)
Type S screens reflect light close to the projection axis twice as intensely as type D and have a mother-of-pearl pigmentation. Within a viewing angle of 30°–40° of the projection axis, the image appears very bright, so a brilliant image can be produced even in very bright rooms. The gain of the screen is 1.7 – 2.4, making it very well suited to outdoor projection.
