The measurement you are looking for is beam intensity. Units of measurement are lux or cd (candela). FYI, 1 lux @ 1 meter = 1 cd. There are a lot of light manufacturers that use the ANSI standard to measure intensity and they would be directly comparable. Since you want a very intense focused beam, you want a very high lux @ 1 meter measurement (or cd). I have a couple lights with a beam intensity over 95,000 cd. My decent throwers are all at least 45,000 cd.