- Gain is the on-axis reflectance compared with a perfectly matte white surface (gain 1.0).
- A screen does not amplify light – higher gain sends more light forwards at the expense of the sides, so it narrows the viewing angle.
- Calculate image brightness with the formula: luminance [cd/m²] ≈ lumens × gain ÷ (π × image area in m²).
- ADEO fabrics range in gain from 0.5 (Reference Grey 2) to 1.2 (Vision White).
- A grey fabric with lower gain improves blacks but needs a brighter projector.
What screen gain is
Gain tells you how much light a fabric reflects towards a viewer sitting on the projection axis, compared with a reference, perfectly matte white surface that diffuses light evenly in all directions. That reference has a gain of 1.0.
- Gain above 1 – the fabric sends more light forwards. The on-axis image is brighter than on the reference, but it darkens more quickly towards the sides.
- Gain of 1 – behaviour close to the reference.
- Gain below 1 – the fabric reflects less light than the reference. This is how grey fabrics work: they lose some brightness but render blacks better, and ALR fabrics also reduce the influence of ambient light.
The key point: a screen does not produce light. Gain does not “amplify” the projector – it only distributes the light differently in space. If it is brighter on axis, it must be darker somewhere else.
Gain of ADEO fabrics – overview
Below are the values given by the manufacturer. The angle is the fabric's catalogue viewing angle.
| Fabric | Gain | Viewing angle | Character |
|---|---|---|---|
| Vision White | 1.2 | 180° | all-round white, darkened and semi-darkened rooms |
| Vision White Pro (temporarily unavailable) | 0.9 | 180° | white with black back, blocks light from behind the screen |
| Reference White 2 | 0.9 | 180° | home cinema, studio, no hot spot |
| Reference White 2 Acoustik | 0.9 | 180° | acoustic, 0.5 mm perforation |
| Ambient Grey 2 | 0.9 | approx. 60° | ALR, standard and short-throw projectors only |
| Ambient Grey 2 Acoustik | 0.8 | 70° | ALR + acoustic, not for UST |
| Vision Acoustik / Vision Macro Acoustik | 0.75 | 180° | acoustic, 0.5 mm / 1.3 mm perforation |
| Ambient Grey | 0.6 | 140° | ambient light, light walls, UST and ST |
| Vision Rear DB | 0.6 front / 0.8 rear | 180° | front and rear projection |
| Reference Grey 2 | 0.5 | 180° | grey, better blacks, suitable for UST |
Full fabric descriptions are on the projection fabrics page and in the guide how to choose a projection fabric.
Viewing angle and half-gain angle
Image brightness changes as the viewer moves sideways away from the projection axis. The industry often quotes the half-gain angle – the angle from the axis at which brightness drops to half the value measured straight on. The higher the gain and the more directional the fabric, the smaller this angle.
In practice it looks like this:
- Fabrics with a 180° angle (Vision White, Reference White 2, Reference Grey 2) give even brightness across the whole room – they can be used in wide conference rooms and classrooms.
- Ambient Grey 2 has an angle of approx. 60°. Viewers sitting close to the axis see a bright, contrasty image despite the light in the room, but someone sitting far to the side will see a darker image. It is a good fabric for a living room with the sofa facing the screen, and less suited to a wide room.
- Ambient Grey (140°) is a compromise: it rejects ambient light less strongly than Ambient Grey 2, but allows wider seating.
Regardless of the fabric, the manufacturer recommends that viewers sit within 45° of the projection axis (a 90° cone).
Hot spot – when high gain gets in the way
A hot spot is a brighter patch in the centre of the image (or where the projector is reflected) that moves with the viewer's head. It appears on directional fabrics, especially with a short throw distance and a large screen, when light hits the sides of the screen at a steep angle. The manufacturer states that Reference White 2 and Vision Acoustik have no hot spot – which is why a 0.9-gain white is the typical choice for home cinemas and studios, where uniformity matters.
How to calculate image brightness – formula and examples
A projector's light output is given in lumens. How bright the image looks to the viewer depends on the screen area and the fabric gain. Approximately:
luminance [cd/m², i.e. nits] ≈ lumens × gain ÷ (π × image area in m²)
You can convert the result in nits to foot-lamberts (fL), a unit popular in cinema: 1 fL ≈ 3.426 cd/m². Illuminance on the screen (in lux) is lumens ÷ area.
Example 1: 16:9 screen, 2.4 m wide, 2000 lm projector
Image height: 2.4 ÷ 1.78 ≈ 1.35 m. Area: 2.4 × 1.35 = 3.24 m². Illuminance on the screen: 2000 ÷ 3.24 ≈ 617 lx.
| Fabric (gain) | Luminance | In foot-lamberts |
|---|---|---|
| Vision White (1.2) | approx. 236 cd/m² | approx. 69 fL |
| Reference White 2 (0.9) | approx. 177 cd/m² | approx. 52 fL |
| Vision Acoustik (0.75) | approx. 147 cd/m² | approx. 43 fL |
| Reference Grey 2 (0.5) | approx. 98 cd/m² | approx. 29 fL |
Example 2: the same projector, 16:10 screen 3.0 m wide
Height: 3.0 ÷ 1.6 = 1.875 m, area approx. 5.63 m². At gain 1.2 the luminance is approx. 136 cd/m², at gain 0.9 approx. 102 cd/m², at gain 0.5 approx. 57 cd/m². A screen 25% wider has approx. 74% more area, so the image is proportionally darker.
Example 3: how many lumens you need – the reverse calculation
The formula can be reversed: lumens ≈ luminance × π × area ÷ gain. For cinema in a darkened room, a common reference point is approx. 48 cd/m² (14 fL). A 2.35:1 Scope screen 3.0 m wide has a height of approx. 1.28 m and an area of approx. 3.83 m².
- Reference White 2 (gain 0.9): 48 × π × 3.83 ÷ 0.9 ≈ 640 lm.
- Reference Grey 2 (gain 0.5): 48 × π × 3.83 ÷ 0.5 ≈ 1150 lm.
These are minimum values in a perfectly dark room. In a room with light the image needs to be noticeably brighter, and brightness headroom is also needed because a projector's output in colour-accurate modes is usually lower than the catalogue figure and falls over time.
Note: the formula gives an approximate result. It assumes uniform diffusion and on-axis brightness. The real image depends on the projector's operating mode, lens settings, light in the room and the colour of the walls.
How to match gain to the projector and the room
| Situation | Direction |
|---|---|
| Dark cinema room, powerful projector | gain 0.9 (Reference White 2) – even brightness, no hot spot; with a very bright projector, the grey Reference Grey 2 (0.5) will improve blacks |
| Large screen, weaker projector, darkened room | higher gain, e.g. Vision White (1.2) |
| Living room with daylight, standard projector | ALR Ambient Grey 2 (0.9, approx. 60°) – viewers close to the axis |
| Ultra-short-throw projector (UST) | Reference Grey 2 or Ambient Grey; not Ambient Grey 2 |
| Wide room, viewers at the sides | fabrics with a 180° angle, e.g. Vision White |
| Speakers behind the screen | acoustic fabrics (gain 0.75–0.9) |
UST projectors throw light at a very steep angle, so a narrow-angle ALR fabric (Ambient Grey 2) is not intended for them – more in the guide screens for ultra-short-throw projectors. Grey fabrics and daylight are covered in the guides ALR and grey screens and a screen for a bright living room.
Common mistakes when choosing gain
- “The higher the gain, the better” – higher gain means a narrower viewing angle and a risk of hot spotting. In a wide room, people at the sides will see a darker image.
- Grey fabric with a weak projector – gain 0.5 means a noticeably darker image than on white. Do the brightness calculation before choosing.
- Comparing gain without considering screen size – doubling the image width means four times the area and a quarter of the brightness with the same projector.
- Ignoring the light in the room – in a bright room, the high gain of a white fabric will not save the contrast; this is where ALR fabric and light control help.
- Ignoring flatness – directional and ALR fabrics show every ripple. A roller screen with ALR needs Tensio tensioning or a frame.
Work out the image size and projector distance in the guide how to match a screen to a projector, and check a complete set-up with your chosen fabric in the configurator.
Frequently asked questions
Does a screen with a gain of 1.2 increase the projector's brightness?
It does not increase the amount of light. It sends more light to viewers on axis at the expense of the sides, so the image straight ahead is brighter and the viewing angle narrower.
What gain for a home cinema?
In a darkened room, a gain of approx. 0.9 (Reference White 2) is the most common choice – even brightness with no hot spot. With a very bright projector, a grey fabric with a gain of 0.5 will improve blacks.
How do I calculate image brightness in nits?
Approximately: lumens × gain ÷ (π × image area in m²). For example, 2000 lm on a 2.4 × 1.35 m screen with a gain of 0.9 gives approx. 177 cd/m².
Why does a grey fabric have a gain below 1?
A grey surface reflects less light, but it also reflects proportionally less ambient light, so blacks are deeper. This requires a brighter projector.
What is the half-gain angle?
It is the angle from the projection axis at which image brightness falls to half the value measured straight on. The higher the gain, the smaller this angle usually is.
