As Pepe Danquart's cheerfully lunatic To the Limit begins, a camera takes in the majestic expanse of Yosemite National Park, gently gliding not just to the edge of a cliff, but over it. What? While not quite great filmmaking, To the Limit is daring enough to appeal to more than just the usual extreme-sports junkies. In profiling the brothers Huber — Alexander and Thomas, Germans who look like Guns 'N' Roses roadies — Danquart and his team of "extreme cinematographers" take as many risks as their subjects: Not content to simply endanger their lives climbing stark precipices, the Hubers are addicted to speed-climbing, an even less safe variant that finds adrenaline rushes in going up perpendicular rocks as fast as possible. The usual extremist blather aside — "If life didn't have risk, it wouldn't be real," nonexplains one climber — To the Limit is equal parts breathtakingly daring rock-climbing footage and family psychodrama. The brothers have good reason to squabble: Thomas introduced his younger brother to the sport, then watched as Alexander seized all the high-profile glory and sponsorships. Still, they're a great team, and the extreme-sports formula never overshadows the Hubers' endearing relationship. Practicing their climb, Thomas yells for motivation: "Good Alexander! Like a little chamois!"