It can be confusing when you are comparing the brightness level of various projectors but they are measured with two different brightness units -- Lumen and ANSI Lumen. So what is the difference between these two units?
"Lumen", in fact, is a more generic term that calculates a device's luminous flux to describe the light output of a light source. It can be known from lumen measurements how much light can be emitted by a projector. In other words, "lumen" is a term to measure the entire light output from the source.
Anker/Nebula adopts ANSI Lumen to list the brightness level of Nebula projectors. "ANSI Lumen" is a measurement unit described and structured by American National Standards Institute to measure the luminous flux of a projector through a common, standard-referenced means, which involves averaging together several measurements taken at different positions. Thus, "ANSI Lumen" is in general more accurate than "Lumen" when used to measure the brightness level of a projector and it is also more widely used in the projector industry.