About Projection Screen Material Gain

Q: Is the projector screen gain higher the better?

SCREENPRO: Whether a higher-gain projector screen is better depends on your specific needs and what you will be using the projector screen for. 
If you need a screen that will be used in a brightly lit room, then a higher gain screen may be a better option.

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Q: What if not in a bright room, but with 10-30% light on?

SCREENPRO: If you use the projector screen in a room with 10-30% light on, a lower gain screen would be more suitable. 
Low-gain screens have a gain factor rate of 1.0 to 1.3 and are designed to minimize the projected image’s brightness. 
They offer a wider viewing angle and lower brightness in dark areas, resulting in darker blacks and a higher contrast experience. Therefore, low-gain screens are a good choice for projecting movies at night or in low-light conditions.

ref:https://www.samsav.com/product/light-rejecting-alr-screen.html