Rew452, you're right there is no standardization on distance from projector to screen when making illumination measurements. The ANSI standards outline many requirements for testing but NOT distance. Even the new standards being proposed by the Society for Information Display
(SID) do not address this issue.
Personally I think it's time that a standard screen size (rather than distance) is applied to ALL projector light measurements. The default size i would suggest is 100" (16:9) since anything smaller than that is just like watching a very large TV set (my opinion of course). The screen would be white and a screen gain of 1.0.
As an example let's take two popular LCD projectors, the Epson 8350 and the Panasonic AR100U.
Working off the Projector Central Calculator
On a 100" screen the Epson has a throw range from 9' 9" to 20' 10". It produces 20 fL at mid range (13' 4").
On a 100" screen the Panasonic has a throw range of 9' 8" to 19' 6". It produces 26 fL at mid range (12' 11").
In the DLP class let's try the Acer H6500 and the Viewsonic Pro8200.
On a 100" screen the Acer has a throw range from 10' 11" to 13' 1". It produces 32 fL at mid range (11' 11").
On a 100" screen the Viewsonic has a throw range from 10' 2" to 15' 7". It produces 29 fL at mid range (12' 4").
If you were to standardize the distance (at say 12') you would end up with varying screen sizes.
To maximize the lumen measurement touted by manufacturers I suspect that all measurements are taken at the closest distance attainable from projector to screen.
For the Epson the closest distance is 6' 2" which produces a 47" screen.
For the Panasonic the closest distance is 8' which produces a 62" screen.
For the Acer the closest distance is 5' which produces a 42" screen.
For the Viewsonic the closest distance is 5' which produces a 41" screen.
I doubt very much we will ever see a TRUE standardization so it will always fall to the consumer to research their projector choice wisely.