What's the difference between ANSI lumens and lumens?
Lumens are a measurement of luminous flux, or the observed power of light. ANSI lumens are measured as per the standards set forth by the American National Standards Institute, which means that the light is measured the exact same way every time. It gives you a more exact figure as to how projectors compare with one another. Other measures of lumens are valid, but they're not as strictly controlled.