The Observational Mode

Observational (objective) mode is best exemplified by the Cinema Verite or Direct Cinema movement which emerged in the late 1950s/early 1960s - it attempted to capture (as accurately as possibly) objective reality with filmmaker as neutral observer.

This is also known as fly on the wall because the camera crew try not to get too involved with the scene because try to keep it as natural as possible so that you see everything that happens there and so that you believe it.

These are more visual documentaries so that you can see how other people live for example.

The observational mode of documentary developed in the wake of documentarians returning to Vertovian ideals of truth, along with the innovation and evolution of cinematic hardware in the 1960s. In Dziga Vertov's Kino-Eye manifestoes, he declared, “I, a camera, fling myself along…maneuvering in the chaos of movement, recording movement, startling with movements of the most complex combinations.” (Michelson, O’Brien, & Vertov 1984) This emphasis on mobility became practicable in the early 1960s as, “new, light equipment made possible an intimacy of observation new to documentary, and this involved sound as well as image.” (Barnouw 1993) The move to lighter 16mm equipment and shoulder mounted cameras allowed documentarians to leave the anchored point of the tripod. Portable sync-sound systems and unidirectionalmicrophones, too, freed the documentarian from cumbersome audio equipment. A two-person film crew could now realize Vertov’s vision and sought to bring real truth to the documentary milieu.

This is a 5 Min. Short Observational Documentary about Edgar, a blind guy who practices Aikido
From this you can see that they try to let him do his own thing and show what the documentary is about. It is a very inspiring video touches many people, as a lot of Observational documentaries do.