It was "filmed" in the era when portable video tape cameras were brand new. The cameras and tape decks were huge, but for the first time ever film makers could shoot hours and hours of material without needing a big crew.
There's so much to recommend about this film:
1. It documents one of the most violent, dangerous neighborhoods in the entire history of the US - the South Bronx in the 1960s and 1970s.
2. It shows a VERY different kind of police work from what we see today.
Yes, these cops are hot dogs (what cops aren't?), but they're largely brave, compassionate, and dedicated to public service.
No bullet proof vests, no SWAT teams, no tanks, no making unnecessary arrests, no pointless hassling of people.
Compare this to the cops today: Bullet proof vests worn all day in totally safe suburbs, SWAT teams to deliver simple summons (often assaulting and sometimes killing the wrong people), and "police work" that consists mainly of hassling people, making "quotas and looking for property to seize (i.e. steal.)