The highest resolution of the Benq SP840 is 1080p (1920x1080). That's over two times the resolution of a WXGA (1280x800) projector, which is the most frequently found resolution.
This multimedia projector's resolution (1080p (1920x1080)) is in fact the best resolution across all 3000:1 contrast ratio multimedia projectors that have been available for a comparable time to the SP840.
Across similar types of multimedia projector the worst resolution is SVGA (800x600).
It may also be worth considering one of the other projectors that have a resolution of 1080p (1920x1080) currently available including the IN3128, or the IN3118 (£1,179.99) both from Infocus which has a better Rating.