[Experts guide the correct choice of cinema-level projection screen] Home projection screen purchase common sense
Installing the right type of screen can have a significant impact on the movie appreciation experience and save money for theater operators.
The screen has several influences on the experience of film appreciation-the most important thing is the quality of the film: brightness, color reproduction and contrast, and distracts attention by potential screen flaws. The screen can also affect the acoustic performance of the speaker system behind the screen, especially the high-frequency loss. The ideal brightness level of the picture is determined by referring to the world-recognized SMPTE standard. The standard stipulates that when viewed from the center position, the brightness of the center of the screen must reach 16 feet Lambertian (55 candles per square centimeter). The minimum brightness of the four corners of the screen is 12 feet Lambertian.
The brightness of the screen that the audience sees depends on several factors: the light emitted by the projection lamp, the light loss from the reflector through the lens and projection window glass to the screen, and the reflected light from the screen. Modern cinema projectors use xenon lamps (compared to the old carbon lamp technology) with various powers. Depending on the size of the screen, the xenon lamp power of most multi-hall theaters is 2.0 kW to 7.0 kW. The greater the lamp power, the greater the light output. Large, but the higher the cost of the xenon lamp, the greater the power consumption.
The screen is the main factor in the brightness of the light reflected back to the audience. The white plastic curtain scatters the light and reflects most of the light to the ceiling and side walls, so it is lost. The screen called 'gain' returns more light directly to the audience. The gain level of the screen is related to the amount of light reflected back, and its measurement is carried out in accordance with the reference standard (magnesium carbide board with a light reflection value of 1). Commercial white plastic screens have different reflectivity, but usually have a reflectivity of 0.8-1.0 according to the reference standard. 'Gain' screens can have a gain level of 2 or higher, but screens used in theaters are usually best at 1.4-1.8 depending on the size of the theater screen. Screens with a width of more than 11 meters usually benefit from using a gain screen. When the screen width is more than 14 meters, it is best to use a screen with a high gain (1.8). A high-gain screen with a gain greater than 1.8 will produce 'hot spots' (that is, the center of the screen looks too bright).
Now some theaters are using digital projection as an option for 35mm film projection. The latest digital projector can output up to 17,000 lumens of brightness. In digital projection, the light output may not reach the brightness of traditional projectors, so when the screen width is greater than 10 meters, the use of a gain screen will benefit.
The white plastic screen is usually installed on a flat screen frame. However, in order to optimize the reflection of light and the viewing angle of each part of the theater, the gain screen is best installed on a curved screen frame. Since the white plastic screen scatters light, if the curved screen frame is used, it will cause the loss of contrast, so it is not recommended. The arc of the gain screen depends on many factors, but a chord-to-height ratio of 20:1 is usually used.