Unlike the residential AV world in which most projection systems are installed in darkened home theaters, the commercial applications for projection are widespread and often in environments where controlling lighting conditions is not ideal.
Integrators and end users have used white projection screens for so long, and we still see them today—even in rooms with ambient light. But really, white screens aren’t a good choice for lighted rooms; they’re very diffusive and spread light in a very wide pattern. They do this with both projection light and ambient light, which then compete at the viewer’s eyes.
Using a high gain white screen will improve system brightness, but contrast will suffer.
That’s why if there is a good amount of ambient light in the room we recommend an ambient light rejecting screen.
Budget concerns in vertical markets like K-12 schools may mean there will always be matte white screens deployed, because they are the least expensive solution. But when budgets allow, there’s no reason not to use an ambient light rejecting material where it is needed.
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However, just going gray isn’t necessarily the answer. Not all gray screens are ambient light rejecting. Some improve contrast thanks to their black tints, but only help a little. They are still mostly diffusive surfaces and don’t “reject” or “reflect” off-axis ambient light away from the audience.
The best ambient light rejecting materials are darker gray to help image contrast, and are more angular reflective than diffusive. These vinyl-based materials use reflective components to reflect off-axis ambient light away at the same angle that it hits the surface—essentially bouncing it away from the audience.
Keep in mind, though, that materials that are the most ambient light rejecting should be used carefully—they are so reflective that hot spotting and narrow viewing cones can become issues. When these conditions occur there are some ambient light rejecting materials available with a good balance of angular reflectance and diffusion that can be used.
How do you know which material to use? There are a couple of questions you need to ask. Assuming you know the screen type and size, you also need to know ambient light levels and the widest off-center seating angle in the room.
Projection screen manufacturer Draper uses an online calculator called the “Projection Planner” to calculate system brightness and contrast. Other projection and projection screen manufacturers may provide similar services, so as an integrator you may wish to consult with your suppliers to aid in system design. Without a tool like this, you are guessing at image quality.
Check out the video of the Projection Planner.
Gray tints do reduce gain in most ambient light rejecting materials and tend to muddy bright colors. You’ll either need a brighter projector to sufficiently “light up” those colors, or better ambient light control.
In the end, though, ambient light rejecting materials typically provide the best solution in lighted rooms, especially when proper selection tools are used to find the right material.
Steve Cook is national AV consultant manager for Draper.
