Gain is the industry term used to measure the amount of light reflecting from a screen surface. No actual light “gain” takes place. Gain measures the screen brightness and directional characteristics.

Every screen product on the market has a "gain" factor. Some screens are "low gain" and some are "high gain." Gain is a measurement of the reflectivity of any screen or projection surface. The gain number represents a ratio of the light that is reflected from the screen as compared to the light reflected from a standard white (magnesium oxide) board.

Lower gain ratings mean the light is reflected more uniformly from the center to the edge of the viewing area. Low gain screens are best for home theater, and with today's brighter projectors.

Matching the projection screen gain with the ambient light and the video projector output is essential if you want to ensure that you will end up with a correct level of brightness for your projected image. The actual level of light reflected from the screen surface, the result must be multiplied by the projector screen gain where a balance of higher gain and greater viewing angle is required.

Gain is measured from the vantage point where the screen is at its brightest, which is directly in front and perpendicular to the screen. Technically the measurement of gain at this point is known as Peak Gain at Zero Degrees Viewing Axis. If you move to the side and view the screen at an angle the brightness of the projected image drops. The angle at which the gain reading drops to 50% of the peak value is known as the Half Gain Viewing Angle. A person viewing the screen from this angle will see an image half as bright as the person seated at the center position.

High lumen output projectors should be matched with lower gain screen surfaces to minimize hotspot artifacts, increase resolution & viewing angles . Projectors with low lumen outputs can be improved with a quality Stewart high gain screen.