We all have seen nice big projector screens that have an image that is just too dim to be clearly seen. To protect against this occurrence, we set a target brightness level during the design process, and we base it on a number of variables. The physical screen size needs to be compared to the amount of light from the projector. This comparison will give us lumens per square foot of screen. The lumens per foot result is compared with a target to determine if the projector is bright enough or even too bright. But how do we determine the target?
As we review the space where the projector is to be hung, we determine the main usage of the space. Additionally, is there a secondary usage that is also important? Some main categories that are used to breakdown the lumens per foot target are listed here: Board room, conference room, small office, digital signage, auditorium, church and classrooms. Each area has a different target. This lends itself to a good starting point on projector brightness.
We have not discussed specific numbers because there is a “but” in all of this. The environment will have a big impact on the target. What may work well in one room may not work at all in another room.
Ambient light is the first consideration when adjusting the lumens per foot target. There are two main sources of ambient light. First is the overhead room lighting over the screen. Will the light generated at the fixture fall directly on the screen or bounce from the walls or floor and wash out the image? If so can this light be removed or turned off? If it cannot be controlled then the projector size and lumens may need to be increased.
The second main type of ambient light is sunlight through open windows. Southern facing windows need to be treated differently from Eastern facing widows. Windows with overhangs to block direct sunlight are treated differently from a glass wall. Window coverings may be translucent or light blocking. Each of these factors needs to be taken into account when adjusting the target.
Another significant factor is the distance between the projector and the screen. In an auditorium it is not uncommon for the projector to be 75’ to 100’ from the screen. This distance is very important since light decreases over distance. A Projector that is 15’ from the screen is treated differently from a projector placed 100’ from the screen.
At Acoustics By Design, we are experts at designing audio-visual systems that meet the needs of our clients. Every project is different, so we make sure the audio-visual design solution takes into account the many factors that influence the end user experience.
