A measurement of light that has been standardized by ANSI. It is commonly used to rate the brightness of a data projector. An ANSI lumen rating uses an average of several measurements taken across the face of the light source. A small room typically requires from 200 to 300 ANSI lumens, whereas a large room may require from 400 to 600. A large auditorium may need 2000 or more.
What is ANSI?
The American National Standards Institute (ANSI) is a private, non-profit organization that administers and coordinates the U.S. voluntary standards and conformity assessment system. Founded in 1918, the Institute works in close collaboration with stakeholders from industry and government to identify and develop standards- and conformance-based solutions to national and global priorities.
Light Output (Lumens) vs. Brightness on Screen (Nits)
Anyone who has looked into projectors on the market knows that lumens is the main unit of brightness that is used in a projector’s product specification. But is knowing a projector’s lumens value alone useful when making a purchase? To answer this question, one must take a deeper dive into what lumens means.
As described above lumen only measures the total light output of a projector, but this by itself is not entirely useful because it does not take into account the reality that the viewer’s eyes are not directed at the lamp itself but at the surface that the projector’s light is being projected on (e.g. a screen). And since a projector’s light reflects off a surface, the size of that surface affects the brightness of the final image. For example, the image produced by a projector that is projecting onto a 1 square meter screen is ten times brighter than if the same projector – with the same lumen value – is projecting the image onto a 10 square meter screen. Thus, simply knowing a projector’s lumen value only offers a partial picture of its brightness since a high lumen value can give a vastly different level of brightness to the eye depending on how far it is spread out.
In that sense a unit such as nits comes in handy specifically because it does take surface area into account. Nits by specifying light in terms of area allows a user to define and compare brightness as it appears on the screen, so that an image that is 300 nits is by definition brighter than an image that is 100 nits.
How to Convert LED Lumen and Light Source Lumen to ANSI Lumen
“Wait…this projector says its brightness is 1,200 lumens while that smaller projector says its brightness is 3,000 lumens, and it’s cheaper? That doesn’t seem right, is there something I’m missing?”
A common refrain for consumers looking for their first projector is to make sure they get the brightest projector they can. But when many of these consumers actually look into the issue, they end up facing a bigger puzzle: how to make sense of the various brightness specifications listed on the market. This issue is a result of the fact that some brands on the market choose not to use the internationally-recognized brightness standard adopted by the majority of their peers, ANSI brightness, but instead advertise brightness specs different from others. Of these various brightness specs a consumer might encounter, the most common are: the aforementioned ANSI brightness, LED brightness, and light source brightness.
Though the standard unit used for brightness, lumens, is used by all three types of brightness, the differences in their definitions cause their values to fluctuate wildly. This results in instances where a projector, such as a BenQ projector, using internationally-recognized standards, might list a brightness value of 1,000 ANSI lumens, while a competing projector, that actually features an equivalent ANSI lumen value, uses LED lumens instead to list a brightness value of 2,400 lumens. The question then becomes: if all of these types of brightness are measured in lumens, why are their values so drastically different?
Difference Between Lumen and ANSI Lumen
Ever noticed the label of your bulb carefully? You may have noted that its light output is displayed in something called ‘lumens’. In the case of a projector, this rating is measured in ‘ANSI lumens’.
The difference between lumen and ANSI lumen is that ANSI lumen is standardized by the American National Standards Institute and is more specific and accurate than the lumen which is standardized by the International System of Units.
Lumen (lm) is the SI unit for measurement of luminous flux i.e. the intensity (in candela) of light emitted per solid angle. ANSI lumen is also used to measure luminous flux but is standardized by the American National Standards Institute and an ANSI lumen rating accounts into consideration the aggregate of several measurements taken for the particular light source according to the area of space that it illuminates.
The reason for introducing a new unit in the form of ANSI lumens is that it usually provides a more realistic brightness measurement since it is well structured and based on a greater number of experimental values.