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Glossary of Common Projection Terms

To help you select and understand projection screen materials, here are some commonly used terms from the projection world and some links to a couple of good resources on

Ambient Light Ambient light is any light in the viewing room created by a source other than the projector or screen (daylight, overhead lighting, hallway lighting, etc.). Ambient light differs in each space and, depending on the space, can be controlled. Ambient light reflects off the screen and washes out the image. The more ambient light there is in a space, the brighter the projector has to be and/or the darker the projection surface needs to be in order to increase the contrast ratio.

Aspect Ratio Aspect ratio of an image is the proportional relationship between its width and its height. The ratio can be calculated from the image’s resolution. For example, 640 x 480 resolution is a 4:3 aspect ratio; 1920 x 1080 resolution is a 16:9 aspect ratio, the international standard for HD. 

Color Shift Color shift refers to the variation of reflected light across the spectrum based on a projection surface that doesn’t reflect light evenly. For example, pure white can be seen with a yellow tint when projected on certain surfaces.

Contrast Ratio Contrast Ratio is the ratio between white and black. The larger the contrast ratio, the greater the ability of a projector to show subtle color details and tolerate ambient light. 

Gain Gain measures screen brightness and directional reflectivity characteristics. This is a technical measurement using 1 as the standard. Higher numbers are higher gain, lower are less gain. Fabric screens have a gain between 0.6 and 1. High output projectors may be needed for lower gain screens. 

Hot Spot A Hot Spot is a bright spot of light from the projector that is noticeable on the screen. Good Rear Projection materials minimize or eliminate hot spots. Some Front Projection materials can have hot spots as well, caused by a shiny or reflective surface. Most fabrics are not good Rear Projection materials because they are thin and show the hot spot from the projector. Aglo is an exception and works well as both Rear Projection and Front Projection with no hot spotting.

Lumen A lumen is a measurement of light or bulb brightness of a projector.

Resolution Resolution refers to the number of pixels making up an image. High resolution images can be projected quite large and still maintain detail. Projectors have a fixed resolution and aspect ratio. Resolution and aspect ratio are usually matched to the content being projected. 

Short Throw Short throw projectors allow users to create big pictures in tight spaces without concerns about shadows obstructing the image or light shining in the presenter's face. These projectors have small throw ratios.

Throw Ratio Throw ratio is the distance from projector to screen compared to the screen size. This ratio determines what size projection screen you can use and how far from the projector to place it in order to have a crisp image. 

Viewing Angle/Viewing Cone The viewing angle is the maximum angle at which a display can be viewed with acceptable visual performance. People within the viewing angle will enjoy the best picture quality while viewers outside of the viewing angle will experience a change in brightness, and possibly color shifting. Some projection materials have wide viewing angles while others have narrower viewing angles. 

Projection Resources: 

Learn which side of the screen should face the audience and other valuable information.

The above link provides a pdf containing a brief summary of when to use each of 54 projection screens, in addition to technical specs on each of their features such as: gain, viewing angle, opacity, thickness, color, material width, and flame retardancy.


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