Gain is a property of a

projection screen A projection screen is an installation consisting of a surface and a support structure used for displaying a projected image for the view of an audience. Projection screens may be permanently installed, as in a movie theater; painted on the ...

, and is one of the specifications quoted by projection screen manufacturers.

Interpretation

The number that is typically measured is called the peak gain at zero degrees viewing axis, and represents the gain value for a viewer seated along a line perpendicular to the screen's viewing surface. The gain value represents the ratio of brightness of the screen relative to a set standard (in this case, a sheet of

magnesium carbonate Magnesium carbonate, (archaic name magnesia alba), is an inorganic salt that is a colourless or white solid. Several hydrated and basic forms of magnesium carbonate also exist as minerals. Forms The most common magnesium carbonate forms are ...

). Screens with a higher brightness than this standard are rated with a gain higher than 1.0, while screens with lower brightness are rated from 0.0 to 1.0. Since a projection screen is designed to scatter the impinging light back to the viewers, the scattering can either be highly diffuse or highly concentrated. Highly concentrated scatter results in a higher screen gain (a brighter image) at the cost of a more limited viewing angle (as measured by the half-gain viewing angle), whereas highly diffuse scattering results in lower screen gain (a dimmer image) with the benefit of a wider viewing angle.

Sources

* {{cite web , url=http://www.projectorcentral.com/projector_screens_gain.htm , title=What is screen gain? , first=Evan, last=Powell , date=May 24, 2004 , accessdate=9 December 2014 , work=Projector Central Display technology