However, within a short time, he had made himself indispensable, not only building sets, hanging lights and moving cameras, but also directing cooking and children's shows.

So Alonzo worked for a time as a still photographer, and as an actor, with appearances in several well-known shows such as Twilight Zone (Season 2 – Episode 12 in "Dust" as Luis Gallegos), Combat!, 77 Sunset Strip, and The Alfred Hitchcock Hour.

This inspiring encounter, as well as the chance to briefly collaborate with James Wong Howe a few years later, finally gave Alonzo the impetus to devote his life to cinematography.

By the mid-1960s, he was photographing many documentaries for National Geographic and the David L. Wolper Company, and greatly influencing the innovative "Look" of the New Hollywood that became so powerful in the late 1960s and early 1970s.

Perhaps his best known student is two-time Oscar winner John Toll, who began his career as Alonzo's assistant on films like Black Sunday, Norma Rae, Tom Horn and Scarface.