Home Theater Projector Buyer's Guide
What Is Brightness?
How much illumination your eyes perceive on the screen depends on two factors: (1) the light output of the projector, and (2) the reflective properties of the screen.
There are two common methods of measuring light in a home theater. One is the ANSI lumen rating of the projector. That measures the light energy being generated by the projector itself. The second is foot-Lamberts (fL), which takes the screen into account and measures the total light that is being reflected back toward the audience. Of the two, foot-Lamberts is the better method to use for setting up your home theater. However, since that number depends on your screen size and screen gain, there is no fL specification published by projector manufacturers.
So how much light do I need?
When it comes to home theater projectors, brighter is definitely not better. What you want is a projector that produces enough light to fill your screen with good contrast, but not so bright that it creates eye fatigue when viewed for any length of time.
It is safe to ignore the published ANSI lumen rating-it is irrelevant for a variety of reasons. Instead, use our Projection Calculator (also available from the left navigation bar) to determine the brightness characteristics of the model you are looking at. It lets you factor in your screen size and its gain rating if you know it. In a dark room, a luminance level on the screen in the range of 12 to 22 fL is in the ideal comfort range, and the calculator defaults to 16 fL to give you a starting point.
In theory, lumens and foot-Lamberts are related. One foot-Lambert of luminance is equal to one lumen per square foot. But there is no direct relationship between the ANSI lumen ratings from the manufacturer and the foot-Lambert measurements as reported in the Calculator. That is because the Calculator factors in reduced lumen outputs for video optimization and average lamp usage, in order to estimate a typical viewing experience.
If you don't want to set up a dark home theater and would rather have some low ambient light, you may prefer to get the screen luminance up into the range of 20 to 40 fL. A brighter picture will help compensate for the loss of contrast caused by ambient light. For each model you may be considering, the Calculator can be used to give you estimates of the screen size and screen gain needed to get that brighter picture.
Don't Get Misled by ANSI Lumen Specs
Whatever you do, don't make any assumptions about a projector's brightness based on its ANSI lumen rating. Some models have video optimization incorporated into their ratings and others do not. That means there are projectors out there which are officially rated at 700 ANSI lumens that are actually brighter than models rated at 1500 ANSI lumens. Spec sheets, as far as lumen ratings are concerned, are meaningless for home theater.