N.B. This article was updated on Mar 28, 2014, and Mar 31, 2015.

A couple of summers ago, I crewed as camera tech on a music video that used Arri Alexa 3-D rigs provided by Cameron-Pace Group. The set was initially overwhelming, but I had the good fortune of working with Richard Moriarty, a supportive camera assistant (AC) who had been in the business for over a decade.

When we had some down time, Richard allowed me to play with our rig's wireless focus assist, which was fine and dandy. Until he caught me looking at our camera's monitor to check focus.

"Don't do that," Richard snapped. I glanced up at him, startled by his proverbial slap on the wrist. "You shouldn't ever look at a monitor when you're pulling focus," he said. "It isn't accurate, and it's not what the production's paying you for."

I didn't fully appreciate it at the time, but Richard's admonishment was one of my best on-set lessons. In the two years since that shoot, I've seen so many camera assistants on student-film sets pulling focus from monitors — which are either mounted on the camera or stationed far away, at video village — that I have to comment on the practice.

Seasoned ACs keep shots in focus using these methods:

  • Measure the distance from the film plane to reference points or actors' marks, with a laser pointer or measuring tape.
  • Use apps or charts to calculate how much depth-of-field they have to work with.
  • Rely on rehearsals and camera operators to make sure everything focus-related works.
  • Stand close to the camera while pulling focus, so they can keep an eye on both the distance marks on the lens barrel and where the actors are moving.
  • Use the "force" (i.e., their talent) when working with a shallow depth-of-field.
  • Most important, their work should be invisible. If a shot is slightly soft, they gradually move to the correct focus mark.

Here's my theory on why younger ACs prefer to pull focus from a monitor. Most of us learned how to take pictures on early digital cameras. While these tools had extremely limited capabilities by today's standards, they did have displays affixed to them. These gave young photographers an idea of how their photos turned out, right after taking them.

It feels natural for filmmakers in my generation to view monitors because they've been trained to look at them for immediate feedback and gratification. But I'm afraid this frame-of-mind has infected the filmmaking process. Now, this topic could lead me down a rabbit hole of on-set politics (who's in control of the final image?) and the "proper" way to direct actors (from video village or from right next to the camera?).

For now, I'll argue that ACs who pull focus from a monitor are: 1) Making their job more difficult for themselves; and 2) Doing a disservice to productions by performing less-than-stellar work.

Monitors tend to distance filmmakers from what's going on in the story and on set. Instead of thinking about story beats and how they'll affect an actor's movements, ACs fill their entire field-of-view with a monitor. There's a reason why great camera operators keep both eyes open while looking through viewfinders: it forces them to be aware of their surroundings.

I've seen first-hand how this separation from story negatively impacts focus. While looking at some dailies on a recent project, I noticed that my AC kept adjusting focus in the middle of a static take, diving forward and backward until it presumably looked sharp on the monitor. I wasn't able to catch this mistake until the image was blown up on a larger screen. Unfortunately, no matter how great the actors' performances were, those takes won't be usable. The AC's reliance on a monitor cost the production money in terms of lost footage.

I believe monitors are only useful to ACs when a camera is on a longer lens and there's an in-frame cue they have to hit for a focus pull. But even then, ACs can avoid this use-case if they're familiar with the script and have a system of communicating cues with their camera operators.

When I'm shooting a project, I feel I've succeeded if my work is invisible. If someone compliments me on a "great shot," I wonder why the shot may have failed in the context of the rest of the movie. Experienced camera assistants feel the same way about their work. A shot that momentarily goes out of focus distracts viewers and takes them out of the story. An AC's primary goal mirrors that of the production's key creatives: to keep audiences invested in the movie until it comes to a close.

UPDATE Mar 31, 2015: Richard Moriarty, the AC I wrote about at the article's beginning, recently gave me another note on pulling focus from a monitor: "You are reactive, not proactive. You are reacting to the buzz in focus." For a contemporary example, watch an older episode of Louie. I love the show, but it's obvious, particularly in those early episodes, when the ACs fish for focus.

UPDATE Mar 28, 2014: Evan Luzi, founder of The Black and Blue, wrote an article based on my thoughts here. The next day, he wrote a follow-up based on readers' comments. I then wrote a follow-up to his follow-up, which Evan worried would create a rip in the space-time continuum.