Classroom Projector Brightness Guide
When you purchase a projector, you are understandably concerned about how bright it is going to be. The brightness of the projector is going to impact how well your students see the images you are trying to transmit.
The goal of this guide is to provide you with information that will allow you to make an informed decision when selecting a projector for your classroom setting.
How Is the Brightness of the Projector Determined?
The brightness of a projector is expressed as ANSI lumens. ANSI is an acronym for American National Standards Institute.
A lumen is a unit of measurement that quantifies luminous flux, or how the output of a light source is perceived. This standard of measurement was created so that you could easily determine the brightness of a projector and compare it with others.
In a typical circumstance, the projector you use in your classroom will need between 2,000 and 3,000 ANSI lumens.
The higher ANSI lumen rating your projector has, the better it will deal with ambient light, be it light coming through the windows or electric illumination.
The light produced by the projector is intense, so you should position the projector so that its light will not shine directly into your eyes or the eyes of your students.
When considering the projected surface, remember that a whiteboard that has a glossy surface is going to cause glare. The more powerful the projector, the greater the glare will be.
Also, projectors create heat. The brighter the projector, the more heat it will create. In order to counteract this heat, most projectors have an internal fan.
This will create noise. The decibel level of the fan will vary, depending on the fan and the structure of the projector.
A lower decibel number means a more quiet projector. As a frame of reference, 30 dB is equivalent to what you would hear in your school library.
How Bright Should a Classroom Projector Be?
There are a number of factors to consider, but we are going to focus on the five primary ones.
This influences how large you will need the projected image to be in order for your students to see it clearly. The larger your displayed image is, the brighter the projector needs to be in order to have a clear image.
A general rule of thumb is that the projector screen should be a height that is equivalent to 16 percent of the distance to how far the students are from the screen.
2. Consider Ambient Light
How dark will your classroom be? A dark room is going to give the best image regardless of how bright the projector is. That being said, a completely dark room is usually not ideal in an educational setting because teachers need to have visual contact with their students, and students need to be able to take notes.
In a classroom where there will be a lot of ambient light, a brighter projector is preferred. However, that same bright projector in a darker room may cause the students to suffer eyestrain. Many projectors have an eco-mode that dims the brightness of the projector by 20 percent.
3. What Is Your Projection Surface?
Modern projection screens have been designed to allow light striking at odd angles to be absorbed by the screen as opposed to reflected by it. This maintains the integrity of the image by eliminating competing light sources, allowing the projected image to keep its high quality and contrast.
A screen can only reflect so much light. How that light is distributed is based on the gain of the screen. A screen that has a gain of one is going to give your students the best viewing angle. Students at the left or right of the screen and those sitting directly in front of the screen will easily see the image. The higher the gain, the brighter the images for those sitting in the center of the room, and the dimmer it is for those sitting on the sides of the room.
This is why it is recommended that you use a screen that has a gain of between one and 1.5 to give your students the best viewing experience. If using a higher gain is a must, discuss the available options with the individuals who install your screens or who supply them.
5. Can a Chalkboard or a Wall Be Used As a Screen?
Yes. But the image quality and brightness may be negatively affected. Projectors designed for classroom environments often have a “Blackboard Mode.” When the projector is in this mode, it attempts to determine the quality of the projection surface and adjust color quality accordingly. Before purchasing a projector of this type, we recommend having a demonstration of the projector to make sure that it meets your needs.