Glossary
Hot spot: a halo of light generated by fabrics that are very reflective in front projection or with high light transmittance in rear projection. The hot-point effect is systematically observed in projection but on a suitable fabric it is hardly noticeable.
Gain: light output, reflectivity or reflection coefficient of the screen.
It is important to make the distinction between the screen's actual gain (ex-factory) and perceived brightness.
Gain is measured with a specific instrument in accordance with international standards.
The gain measurement is taken in the centre line (90°).
Gain reduces more or less quickly the further it gets from the centre line.
It will reduce slightly if it is a matt white fabric and greatly if it is a highly reflective fabric.
Perceived brightness depends on several factors:
- the source (power of the lamp expressed in Lumens).
- the distance between the screen and the projector.
- the screen's gain or reflection coefficient.
- the angle of vision in relation to the screen.
- the lighting environment.
Other factors, such as a screen or lamp's state of repair, also affect perceived brightness.
The ideal brightness for a screen for a film theatre, according to the SMPTE standard, is 14 ft. Lamberts (55 candela per m²) at the centre with a minimum of 12 and a maximum of 22 ft. Lamberts for the 2D projection. At the edges of the screen, brightness must not be below 75% compared to the centre of the screen (and a minimum of 10ft. Lamberts).
In rear projection, the gain (or light transmittance) is calculated in the same way.
Acoustically transparent (perforated or micro-perforated):
Our cinema and home cinema fabrics may be perforated. This option enables sound to pass through the image and therefore add an additional dimension to the video. The three front speakers are placed behind the fabric. We offer three perforation sizes for cinema: standard, with 1mm holes, and micro, with 0.5mm perforations. For home cinema, super micro-perf has 0.5mm holes but at a greater concentration.
NEW : The new acoustic Woven Sound Frabic is an alternative to the Super Micro Perforated screen surface. She offers an enchanced acoustic performance with less acoustic attenuation especially for higher frequencies, while the gain is lower than a matt white PVC surface.
Matt white fabric: white projection fabric with a gain close to or equal to 1. A fabric that is regularly used, whether for cinema, home cinema or meeting rooms, this reflects the light in a uniform way (low light loss at the edges, minimised hot spot).
Colorimetry (or a projector's colour space):
A quality projection fabric with good colorimetry is capable of sending colours faithfully and neutrally. It can be measured easily.
After a certain time, depending on usage and storage conditions, a yellowing of the fabric may be observed.
High-Contrast Fabrics: neutral grey for front projection, accentuating contrasts whilst respecting colour. Slightly high gain of 0.8.
Pearl fabrics: fabrics covered with a coat of pearlised paint to increase gain (from 1.4 to 2.2).
3-D stereoscopic projection:
Embossed projection method with two projectors, fitted with linear or circular polarising filters .
The most efficient technology is circular polarisation, as it is not hindered if the glasses are slanted (ReaID 3D).
Our Victorine 3D and Clarus XC (170, 220 or 270) grey metallic fabric (silver-based) is recommended for this type of projection as it preserves polarisation and, apart from its high gain, compensates for the loss of light caused by the glasses.
On the other hand, the Victorine 3D metallic fabric is not advised for 2-D projection. This method is also called passive 3-D projection, projection in polarised light with the use of so-called passive polarised glasses.
3-D active projection: 3-D projection is made possible thanks to the time offset needed for so-called active glasses made up of LCD panels (also called Shutters). It also requires the use of a housing in the projection box which synchronises the blanking of the glass lenses with images from the projector (Xpand system).
Type of fabric: Cinecitta Super Mat Perf or Victorine perf.
This technology is also used for home cinema. Nvidia markets a 120 Hz 3-D Vision kit.
The display of the right and left images is synchronised with the glasses using an infra-red transmitter.
We recommend our matt white Cinecitta fabric or Starlight fabric for this kind of 3-D projection.
Super Blanc [Super White] fabric: a matt white fabric painted with an ultra-matte paint. Invisible seams.
Rear projection: video projection from the rear. The projection screen is positioned between the projector and the spectator.
Front projection: video projection from the front (the most common).
The moiré effect: the moiré effect in video projection is characterised by deformation of the image. The image has parallel lines crossing through it. Image distortion is characteristic of digital projection on a perforated or woven acoustically transparent fabric and results from the pixels and the holes matching up. So a perforation is recommended that is suitable for the application, depending on the screen's dimensions, projection distance and type of projector used.
Digital projection: Projection using a digital projector suitable for reading DCP {Digital Cinema Package) digital content on a hard disk or downloaded on a server.
Digital cinema: or D-cinema, referring to digital projection.
Pantograph: this term is used to describe the hinged system (also called "scissor" which is fitted to some portable screens (ButterFly) and some ceiling brackets for projectors(..).
Fastfold: a generic term commonly used to designate a foldable portable screen with a stretched fabric fitted with press studs.