Focus for video
In photography you focus, shoot and you're done. In video, focus has to follow someone who's moving, for seconds or minutes, and any hesitation shows. That's why focus is one of the skills that most separates amateur video from polished video.
Continuous autofocus and tracking
For video you almost always use continuous autofocus (AF-C): the camera keeps readjusting focus all the time. Today's cameras detect faces, eyes, animals or vehicles and track them quite reliably.
Settings worth knowing:
- Focus area: for interviews, a wide area with face detection; in shots with several people, a smaller area on whoever matters.
- Transition speed: how long focus takes to move from one point to another. Slow looks more cinematic; fast is more useful for sports.
- Tracking sensitivity: set low, focus doesn't get distracted if something crosses in front; set high, it jumps straight to the new thing.
When autofocus hesitates, focus goes in and out searching for the point, which is called focus hunting or breathing. It happens in low light, low contrast or with very detailed backgrounds. If you see it, switch to manual or lock focus.
Manual focus with aids
In shots where the subject doesn't move, like a seated interview, a product or a static shot, manual is more reliable: focus doesn't change unexpectedly.
- Focus peaking: the camera paints in-focus edges in color. It's the most useful aid.
- Magnification: zooms into the image so you can check focus on the eyes. Remember to go back to the normal view before recording.
If you're using a zoom lens, zoom all the way in on the eyes, focus and go back to your framing. With "parfocal" lenses focus stays put. With many photo zooms it doesn't quite, so check it.
Depth of field with movement
With a very wide aperture (f/1.4, f/1.8) the background blurs a lot, but the sharp zone is very narrow. If the person leans in two inches (5 cm), they're out of focus. In video, a slightly narrower aperture (f/2.8–f/4) gives you a margin you'll be grateful for, especially in manual.
| Situation | Suggested aperture | Why |
|---|---|---|
| Seated interview, one person | f/2–f/2.8 | Soft background and some margin if they move |
| Two people at different distances | f/4–f/5.6 | So both are sharp |
| Walking vlog with a wide-angle lens | f/4–f/8 | Everything sharp, without relying on AF |
| Product extreme close-up | f/2.8–f/5.6 | At close range depth of field shrinks a lot |
Rack focus
A rack focus (or focus pull) shifts sharpness from one point to another within the same shot, without cutting. It's a way of directing the viewer's eye: first we see the hand putting down the letter and then, in the background, the face of the person who's going to read it.
How to do it:
- Wide aperture so the difference is noticeable.
- Mark the two points: in manual, with tape on the focus ring or by memorizing the position; with autofocus, by tapping the screen on the target point.
- Rehearse the speed: the shift should follow the action, not get ahead of it.
In film, one person does nothing but focus: the focus puller, or first assistant camera. They measure distances with a tape measure and turn the ring with a remote control. If a shot comes out soft on a professional shoot, it's on them.
- Continuous AF with eye detection for moving subjects.
- Manual with focus peaking for static shots.
- Don't open up all the way if you don't need to: in video, focus margin is gold.
- A rack focus directs the eye without needing a cut.
Your turn: your first rack focus
Put an object close to the camera (a mug) and a person 6 to 10 feet (2 to 3 m) away. Film a shot that starts focused on the mug and ends on the face.
- Use the widest aperture you have.
- Do it first in manual and then by tapping the screen.
- Repeat until the shift takes about two seconds and is smooth.