Choosing a screen for an ultra short throw projector

A UST screen is not a projector screen with a different label

An ambient light rejecting screen does not reject light in general. It rejects light arriving from one direction and accepts light arriving from another, and which way round that is depends on where the projector sits. A ceiling-mounted projector throws from in front and above, so a conventional ALR screen is built to accept light from there and reject light from the room. An ultra short throw sits on the floor or on a cabinet and throws upwards from below, which is the opposite geometry.

XGIMI describe their own UST screen as capturing light from the projector beneath it while rejecting light falling from above. Put a conventional ALR screen in front of a UST and you have bought a surface engineered to reject the one light source you want it to keep. It is not the cheaper version of the right product. It is the wrong product.

• A UST ALR screen is built to accept light from the projector below it and reject light falling from above. Richer Sounds
• The XGIMI screen's surface is specified as ambient light rejecting for ultra short throw. Richer Sounds

Viewing angle is where the mismatch shows up

The number that exposes this is viewing angle, and the gap is not subtle. Vividstorm specify 170 degrees for their UST screens. Screen International specify 60 degrees for the ALR cloth on their Modigliani fixed frame, which is a fine screen for a ceiling-mounted projector in a dedicated room.

Sixty degrees is roughly thirty either side of straight on. In a living room where people sit along a sofa and across an armchair, that is the difference between everybody seeing the picture and two people seeing it while everyone else looks at something grey.

• Vividstorm specify a 170 degree viewing angle. Richer Sounds
• The conventional ALR cloth is specified at a 60 degree viewing angle. Projectorpoint

An ALR screen dims the picture on purpose

Both Vividstorm screens specify a gain of 0.6. Gain is measured against a reference white surface at 1.0, so 0.6 means the screen returns rather less light to the viewer than a plain matte white one would. That is the mechanism rather than a defect: the structure that throws room light away also throws some of your projector's light away.

The practical consequence is that an ALR screen and a bright projector belong together. It is why the brightest machines in this category are the ones sold for rooms you live in, and why pairing a dim projector with an ALR screen is the worst of both choices.

• The UST ALR surface is specified at a gain of 0.6. Richer Sounds

If the room goes properly dark, you may not need one at all

ALR earns its money when you cannot control the light. In a room you can make genuinely dark, a good matte white surface will give you a brighter and more neutral picture for a fraction of the cost, because there is no ambient light to reject and no reason to accept the gain penalty for rejecting it.

This is the question worth answering before spending anything: will you watch with daylight or lamps on, or not. A basement or a room with shutters usually falls on the cheap side of it.

How it mounts matters more than it sounds

Three shapes exist and they suit different rooms. A fixed frame is the cheapest and the best picture, and it is a permanent object on your wall. A drop-down rolls out of a housing above the screen wall, which still means something fixed overhead. A floor-rising screen lifts out of its own cabinet on the floor and drops away afterwards, which is the one to know about if the ceiling is low or the room is also used for other things.

Vividstorm's floor screen is specified as electrically retractable, free standing and tab tensioned. Tab tensioning is the part that keeps a retractable surface flat, and a retractable screen that is not tensioned will show waves that no projector can correct.

• The floor screen is electrically retractable, free standing and tab tensioned. Richer Sounds
• The drop down screen is electrically retractable and tab tensioned, without the free standing cabinet. Richer Sounds
• The XGIMI screen is a fixed frame, and sits 17.8cm from the projector. Richer Sounds

What you can actually buy

This is a thin market and it is worth knowing that before you start looking. Our own survey found six UST screens from two makers at the retailer we price from, and every one of them was pre-order rather than in stock when we checked. The prices below are what they ask, not what the market will settle at, and the generic ALR cloth is listed only to show what the wrong product costs.

The shortlist

Projectors we have judged for this

• Hisense L9Q Laser TV £3,999
• Hisense PX3-Pro £1,799