Screen surfaces are characterized by their gain, viewing angle and contrast. They are often made of complex materials specifically engineered and tailored to a particular application or projection method.
In the sections below, we explain in more detail.
Screen Gain relates to how bright the projected image will appear. The greater the gain, the brighter the image will appear. The industry standard of 1.0 gain is determined from the brightness of a black of magnesium carbonate.
Gain values can be compared relatively. For example, a screen with 1.5 gain will produce an image 50% brighter than a screen with 1.0 gain.
With today's high output projectors, having high gain is not as important as it once was. Nevertheless, for low output projectors or when projecting in a fully lit room higher gain screen surfaces should be considered.
Screen Viewing Angle is measured from the projection axis and extends in all directions to form a viewing cone with the tip of the cone touching the screen surface. Within the viewing cone, the audience will experience optimal image quality. Outside of the viewing cone, the image is still visible, just not optimal.
The figure at right shows a 2-dimensional view of this. The viewing angle is represented by the greek letter theta. The bottom line here is that anyone between the two blue lines will see the optimal projected image.
Viewing angle and gain are interrelated. In general, screens that distribute the reflected image over a wider viewing angle have lower gain. Screens with higher gain concentrate the reflected image within a narrower viewing cone to achieve the additional gain.
When choosing a screen surface, consider your audience layout to help determine acceptable viewing angles. Will the audience be spread widely to the left and right of the screen or will they form a narrow but deep arrangement in front of the screen?
The left-hand figure shows the situation where the audience is shallow and wide, while the right-hand figure show a narrow but deep audience. In terms of viewing angle, the toughest customer in the audience is the person sitting at the end seat in the front row, since that person needs the widest viewing angle of anyone.
Let's get Mathematical
In the figures above, the angles theta-1 and theta-2 are the MINIMUM viewing angles needed for each audience. So how can we calculate those angles?
First, measure the distance from the screen to the first row of the audience, then measure the width of the audience. In the figure at right, these are shown as D and W respectively.
The angle theta is then calculated from the arctangent of W/2D. Remember that the angle theta is the MINIMUM viewing angle.
No arctangent button on your calculator? No sweat. Use Google as your calculator! Let's say you calculated W/2D as 1.5. Just type "arctangent 1.5" in any Google search box and Google will do the rest.
Just make sure to multiply the answer by 57.3 to convert from radians to degrees. Heck, you can do that in Google as well. See below for sample output from Google.
OK, now that we made it past that topic, we can tackle the less complicated concept of contrast.
Contrast is related to the difference between the whitest whites and blackest blacks in the projected image. The larger the difference, the higher the contrast. Typically, projection screens have no problem reflecting the white end of the spectrum, but struggle to faithfully reproduce the black end.
To address this issue, Da-Lite and Draper both offer High Contrast screen surfaces, which improve black levels while maintaining the bright white levels. This is achieved through the use of a reflective gray surface.
Would you benefit from High Contrast? We think High Contrast screen surfaces are best suited when projecting TV/movies or high-end photography where deeper blacks add to the cinematic or artistic experience. On the other hand, if you're projecting Powerpoint presentations, you probably won't see the value.
See Other Resource Pages
- Choosing the Best Screen Size
- Choosing the Best Screen Format
- Da-Lite Screen Surfaces
- Draper Screen Surfaces
Clear as Mud?
Feel free to contact us with any questions.