Digital Projectors Dim?

This seems kinda whack:

To get the necessary brightness on such large screens, they'll be aiming three digital projectors at each screen.

--CinemaTech: `Cars' premiere in Charlotte: Biggest digital debut ever...outdoors

Three projectors? Isn't there any way to up the brightness in a single projector? Anyway, the vibrancy of the image looks like it's going to be a big selling point with Cars. The way the movie is lit is photorealistic in a lot of places. Combine that with talking cars and you have... an uncanny valley.