Click to enlarge. SO close
The LG CF3D projector offers more brightness in 3D than any of the low cost 3D projectors. Although I was tempted to try to measure the brightness through one of the lenses of the passive glasses, I couldn't convince myself that it would be a valid measurement. Forgetting that, I conclude that this claimed 2500 lumen projector, first of all, gets very close to its claims. We know that 3D is going to wipe out an absolute minimum of 50% of the brightness (since you are only seeing one eye at a time), but how much more, we really don't know.
For practical purposes, I am assuming for now, that a system like the LG CF3D is going to lose about 60% of lumens. That means the CF3D, is going to output close to 1000 lumens in its brightest mode, while doing 3D!
Having owned a projector dealership for a great many years, I can report that it was less than 10 years ago, that portable projectors started reaching 1000 lumens. At the time, we all discovered, that 1000 lumens was enough to fill a typical conference room screen - 5 or 6 feet diagonal, even with a healthy dose of fluorescent lighting on.
In other words, 1000 lumens, in small, and even some medium sized rooms, has been enough to do good work, without killing the lights - essentially modern projection. As often said, you can never have too many lumens (well almost true), but the point is, the LG does have enough lumens to do nice sized projection for working groups, board rooms, and most presentations for less than 50 people. Remember, with a little more lighting control, the LG can do a respectable job on a screen in the 100" diagonal range, and still not be a pretty dark room. That's what people want, and the LG delivers!