Projector screen vs painted wall vs ALR screen: which do you need?
A painted wall works in a dark room. A screen earns its cost in light, and an ALR screen must match your projector's throw. Here is how to choose.
Can you use a painted wall instead of a projector screen?
Yes, in a room you can make dark, and plenty of good home theaters do. A projector puts light on whatever is in front of it; a screen's job is to send that light back evenly and, for some screens, to reject the light you did not ask for. A smooth wall painted in a flat (matte) finish does the first job reasonably well. What it gives up: any wall texture shows as a faint pattern on bright scenes, a sheen finish creates a visible hot spot where the projector's light reflects, there is no black border to frame the image and absorb overscan, and paint has no way to reject room light. If the wall is smooth, the room is dark and the budget is better spent on the projector, a painted wall is a reasonable start you can always replace with a screen later.
What does screen gain mean, and does paint have it?
Gain is how much light a surface sends back toward the seats compared with a reference white surface, rated 1.0. Above 1.0 the image is brighter for viewers on the projector's axis and dimmer for those off to the side; below 1.0 the surface gives up brightness, usually to reject ambient light or to deepen black. Real screens in our catalog state their gain: the Elite Screens CineTension2 states 1.0, the Silver Ticket STR-169120-HC high-contrast grey states 0.95, and the Sable Frame CineGrey 3D ALR material states 1.2. We do not track paints, so we cannot state a gain for one. If a paint advertises a gain, treat it as an unverified claim unless the maker says how it was measured. One thing is predictable: a paint does not reject directional light the way an ALR screen's surface does.
Does grey paint or an ALR screen fix a bright room?
Grey paint helps a little, and an ALR screen helps more, but neither replaces controlling the light. Grey lowers how much light comes back from the whole surface: blacks get deeper, but whites get dimmer by the same proportion, so the contrast between the picture and ambient light hardly changes. An ALR (ambient light rejecting) screen is different because its surface is directional. It returns light arriving from the projector's direction and rejects more of the light arriving from elsewhere, which is why it can hold contrast in a room with some light. The cost is usually a narrower viewing angle, often with gain near or below 1.0 (most of the UST and CLR screens in our catalog state 0.6 to 0.9). And ALR screens are not interchangeable: which one works depends on where your projector sits. For the projector side of a bright room, our bright-room projector guide ranks the brightest models we track by stated lumens.
Which ALR screen does an ultra-short-throw projector need?
A UST-specific one, and this is the rule that runs only one way. An ultra-short-throw projector sits under the screen and fires steeply upward, so its screens (CLR, ceiling light rejecting, or UST ALR) use a ridged surface that accepts light from below and rejects it from above, where ceiling lights are. The invariant our catalog is built around (spec §4.5): CLR and UST-ALR materials pair only with UST projectors. Put a conventional projector, which throws from across the room, on one of those screens and the picture comes back dim and uneven, so the builder flags that pairing as an error. The other direction is softer: a UST on a plain screen or a painted wall works, and gives up only resistance to room light, which in a dark room may not matter. The Elite Screens Aeon CLR 3 states 0.8 gain, typical of this class. Our UST and ALR screen guide goes through the material types in detail.
When is a real projector screen worth it over a painted wall?
When the room has light you cannot control, when you use an ultra-short-throw projector, or when the speakers need to go behind the image. A multipurpose living room with windows is the case for a light-rejecting screen; a UST projector is the case for a UST-specific one, as above. Speakers behind the picture need an acoustically transparent screen, a woven or perforated surface that lets sound through, and the projector screen hub has an acoustically transparent filter for the screens whose sheets state it. A dedicated, dark room with a smooth wall is the case where paint is a genuine option. Whatever you choose, size it for your seating distance first: the screen size and seating distance guide does the math, and the projector throw distance table shows how big an image the projectors we track throw from where you can mount them.