Q: I keep seeing the word "gain" in projection screen descriptions. What does it mean and is it important?

A: To over-simplify it; the higher the gain the brighter the image on that screen.

A projector screen works by reflecting the light back from your projector to your audience's eyes.

The brightness of the image reflected back off of the screen's surface is measured in units of "gain", gauging the reflectivity of that surface.

The gain number represents a ratio of light that is reflected back from a surface from a light source. This ratio is in relation to the light reflecting off of a block of either barium sulfate or magnesium carbonate, serving as the industry's standard for a gain of 1.0.

Gain is measured from the vantage point where the screen appears to be at it's brightest. This is generally the very center of the screen, directly in line with the projector. This is at 0° and known as the "Zero Degree Viewing Angle". As you move to either side of this position the brightness of the projected image may start to diminish. The point at which the brightness diminishes to 50% brightness from the measurement at the Zero Degree Viewing Angle is known as the "Half Gain Viewing Angle".

A viewer outside of this viewing angle (also known as viewing cone) will see the image at half the brightness as the audience inside of the cone.

A screen with a gain measurement of greater than 1.0 infers that the image projected back off of the surface is brighter than the image being projected at the surface.

For example; a projector screen with a gain of 1.5 will project back the light 1.5x brighter than the light being projected at the screen. A 1,000 lumen projector aimed at a screen with 1.5 gain will be perceived at 1,500 lumens. The screen achieves this by focusing the light into a more narrow reflective angle, instead of uniformly reflecting the light in all directions. This is why higher gain screens have a smaller viewing angle.

A projector screen with a gain measurement of .8 will reflect back at 80% of the original brightness. That same 1,000 lumen projector will be viewed by the audience at only 800 lumens.

Some projection surfaces also have a "Vertical Half Gain Angle". These surfaces are generally ambient light rejecting surfaces which require specific placement of the projector in order to achieve maximum brightness for the intended audience while diminishing the ambient light hitting the screen's surface.