Here’s How You Can Measure Distance for Focus Marks

Have you any idea why the 1st assistant camera (AC) is also known as the “Focus Puller?” It’s due to the fact that the single responsibility of keeping any subject in focus is amazingly admired, and not to mention, there’s a whole career devoted to it.

Know that focus pullers as well as 1st AC’s have a lot more to do than just spinning a disc which is attached to a lens for 12 hours each day, but this single task seems to be more valuable contribution addition that we can grant to make a film.

But you won’t be able to pull focus without having it measured for it, so here’s how you can flash out a tape measure on set, so you know what you’re up to.

How can you measure focus marks?

Start at the Film/Sensor Plane

The measurement for any shot begins at the film/sensor plane of a camera resting behind the lens. Know that its true location is designated by a “Phi” marks on the camera’s body.

When you’re using ENG (Electronic News Gathering aka TV/Broadcast) lenses, this is the only time when you won’t be able to measure from the film/sensor plane. These can easily be recognized by a green stripe around the barrel. With ENG lenses, you measure from the lens’ front.

Measure to Each Subject in the Scene

The subject you’re focusing to will be the next point of measurement. Are multiple subjects in a scene? If yes, know that considering many measurements will be beneficial to you. Most of the time the subject is a character, but frequently it’s not. No matter what the subject is, you’ll have to measure up to the part you want in focus.

Why should you measure for focus?

As you know that focus is set and driven through distance, you’re significantly telling the lens which light rays should be focused on a film at a certain distance or sensor plane, that too without having to get into lens optics.

Can your eyes ever be as precise as your tools? We don’t think so. Well, you can become an expert when it comes to guessing distances, but don’t forget that you’ll never be as accurate as a trusty tape measure. Don’t forget that guessing the distance and knowing the distance are two different entities when it comes to pulling follow focus.

And what can be the most reliable way to keep a subject in focus, even to this day? As long as the back focus on a camera is functioning in a proper way, you won’t have a subject standing at 8 feet out of focus on setting the lens to 8 feet. As simple as that!