There's more. Eco mode surprised me. We find most Epson's down 25-30% when switching to Eco mode, but the G7905 only looses a fraction more than 20%, a number that should be true, no matter which mode is measured.
Eco Mode on G7905: 5807 lumens
Measured in Dynamic mode, wide angle on zoom
Effect of Zoom Lens on Brightness:
Epson's standard zoom for this projector, has a 1.6:1 zoom ratio. For a zoom of this range, performance was good, with only a minimal, almost 3% drop in brightness going from full wide angle (closest positioning of the projector) to mid-zoom.
Better still, moving to full telephoto - furthest placement from the screen, the Epson measured only 17.7% lower than full wide angle.
In Dynamic mode, at full power, that worked out to 5975 lumens.
Remember, other zoom lenses will have their own characteristics. Expect the very long throw zoom lenses to be visibly less bright (as is typical with longer throw lenses, as any serious photographer knows).