Selecting the Proper Screen Material for Your Application
Have you ever used a screen material other than white for a projection application? If so, what color? Light gray, dark gray, or even black? What effect does screen color have on your projected image? What about the effect of the screen surface and material from which the screen is made?
To solve these questions, our Application Support team projected video in an ambient lit room onto a screen that was white on one side and gray on the other (see figure below).
The left side of the screen is matte white while the right side of the screen is a dark shade of gray. In this ambient lit environment, the gray screen material produced a more vivid image. The gray side of the screen uses a material with angular reflective properties (see description below). The fact that the material is gray helps to preserve black level, even in the presence of ambient light. This increases the perceived contrast of the image, making it look as if it has more detail and resolution than the white section of the screen, which appears more washed out. Screen selection plays an important role in how you design for a projection application, so let's take a closer look at these material types.
A matte white screen is typically described as having either unity gain or a gain of 1.0, and is an evenly diffusive material. That means when light from the projector reflects off the screen, it diffuses evenly in all directions (see figure below). However it is important to note that when ambient light reflects off the screen it also diffuses evenly in all directions including back at the audience. Thus making the image from the projector look dim or washed out.
Angular reflective screen material, which is typically dark gray, is often a better choice when designing for ambient light applications. With an angular reflective material, light hitting the screen reflects at an opposite angle. Projection light bounces almost straight back to the audience, while ambient light at more extreme angles bounces away from the audience (see figure below).
For projectors to be an effective solution for media rooms, careful selection of the screen material is vital. DP has performed preliminary testing with angular reflective screens and has found results to indicate the following rule of thumb: 2000 lumens of light output produces great looking images on 16 sq feet of screen material in venues with typical ambient lighting. 2000 lumens per 16 sq feet equates to 125 Foot Lamberts, if the screen was unity gain.
Put another way, for typical general-use ambient light environments:
• A 2500 lumen projector (M-Vision, dVision, HIGHlite Cine HC class projectors) will produce great imagery on a 6' x 3.375' angular reflective screen.
• A 4500 lumen projector (dVision, HIGHlite, TITAN single lamp class projectors) will produce great imagery on a 8' x 4.5' angular reflective screen.
• A 7000 lumen projector (E-Vision, HIGHlite 660, TITAN class projectors) will produce great imagery on a 10' x 5.625' angular reflective screen.
• A 10,000 lumen projector (TITAN Dual class) will produce great imagery on a 12' x 6.75' angular reflective screen.
• A 16,000+ lumen projector (TITAN Quad class) will produce great imagery on a 14' x 8.875' angular reflective screen.
Typical general use ambient light environments are defined as multiple types of indirect artificial lighting, but no direct light falling on the screen, and no sunlight pouring into the room.
Although this is just a rule of thumb, we believe it provides a good guideline. In an ambient lit application, front projection adds value by offering image sizes far beyond what a flat panel can provide. When paired with an angular reflective screen, DP's product line can accommodate large to giant image sizes in a wide array of ambient light environments.
Contact our Dedicated Applications Support
For additional support with projection applications please contact DP's Applications Support team at 770-420-1350 or send an email to firstname.lastname@example.org