After a premiere at the Tribeca Film Festival this spring, documentary “Talihina Sky: The Story of Kings of Leon” is ready for its national debut, as the band’s fame continues to grow internationally. Showtime has nabbed the rights to the feature-length film, and will air it on Aug. 21 at 10 p.m. EST/PST.

First-time director, fan and friend Stephen C. Mitchell focused the camera in on celebrity as much as it did the music of brothers (and cousins) Followil, following the gawky blue-screened embarrassments of their pre-rock days to the arena-filling moments preceding the start of their latest album “Come Around Sundown” (2010).

Read my review of the film here, as well as the interview with three-quarters of Kings of Leon following the movie’s debut.

For Mitchell, there was never a big debate over what boundaries he set between being the band’s resident video archivist and their pal. In fact, one of “Talihina’s” centerpiece moments was nearing the end, when it’s clear frontman Caleb Followill had had a few, and it seemed the pair were just riffing, having a heart-to-heart.

“We were both f*cked up,” Mitchell told me in an interview this April. “We had a work day that day, and as we were leaving the studio, he said, ‘Come over tonigh and let’s knock down an interview. I did, but Iwasn’t prepared. I just set up a camera on a tripod, mic’ed him up and just sat on his back porch, the two of us. We just drank wine and smoked some pot and hung out and talked. He just kinda spilled it… to me, it was like he was talking just to me, but for the audience, it was like he was talking just to them.”

Still, Mitchell said, the guys were never acting for the camera; they were “acting up” for the camera. “Half the time, I think all they really wanted to do is just get me to laugh.”

[Jump...]

The close relationship Mitchell forged with the band started before there even was a band. Nathan and Caleb were signed to a music publishing deal to Windswept-Pacific (now under Bug Music), where Mitchell used to work. About a year after that, Jared and Matthew joined up to make up the whole band; Stephen had already befriended the guys and even started showing up at the Followill family reunions with a camera.

“We were filming very early, like when they were still in the garage and literally putting their first songs together,” Mitchell said. Lamentably, those earliest clips were stolen when the band’s van was broken into years ago. “We lost all that footage. So maybe someday it’ll all come out we’ll be surprised if it comes out online.”

Still, the Followill family, the band’s label, fans and others have helped to fill in those gaps, footage from the earliest tours to the U.K. to road trips to Followill family Christmases. It amounted to more than 700 hours of tape – containing material that was even tough for the band or its audience to watch, like scenes of in-fighting, drunken debauchery and aforementioned familial silliness.

“Who’s perfect? Rock stars aren’t perfect,” Mitchell said. “But everyone gets all wound up about the guys fighting. Brothers beat the sh*t out of each other. It’s what you do. There were brawls where I couldn’t film because we were trying to get out of the way or we were trying to get them separated.”

It comes with the territory of playing confidante and band historian.

“There was a lot of trust in place. The boys… are the exec producers, and they ultimately wanted to know everything we chose to show people in the final product. That was it… I’m very lucky. I had a great story, found a pretty good cinematographer, the guys had enormous resources. It was once-in-a-lifetime access, more than once-in-a-lifetime. Those guys made my dream came true.”