Depth of field when filming interviews
Everyone loves filmic out of focus backgrounds, but using large sensor cameras to shoot talking head interviews isn’t as simple as people think.
I’ve put this article together to help people with little or no experience and veterans who are just too proud to admit they need help. The aim is to give you a fighting chance to achieve critical focus in real life situations.
TV is littered with documentaries were camera ops simply haven’t achieved perfect the focus. This is sad to see as many of the docos are high profile one-off situations that will be around for some time.
I often see people trying to shoot interviews with a depth of field of just a couple of inches. They are constantly adjusting focus as the subject moves backwards and forwards throughout the interview. Trust me, it’s almost impossible to maintain critical focus in HD or above by viewing the small LCD panel of a camera, whether it be a high-end cinema camera or a DSLR.
What is Depth of field?
Put simply depth of field (DOF) is the area of a scene that is in focus. Anything in front or behind this area will be blurred to a greater or lesser degree.
Depth of field is often seen as just a creative tool, but used correctly, it can make your camerawork much easier.
Maintaining good focus outdoors is a particular problem, as the camera LCD screen/monitor often can’t be seen clearly in sunlight. It’s not always practical to set up monitors in a fast run and gun situations (I hate that expression but you all know what it means).
How to assure great focus?
You have to take control of your depth of field by choosing an aperture that gives a reasonable DOF instead of just a few inches.
Lens choice, aperture and subject distance, determines the depth of field size, but as a general guide, wide lenses such as a 28mm will give a deeper DOF than say an 85mm telephoto lens.
Take a look at the visualizer video below and see how ‘aperture size’ changes depth of field. The video is for illustrative purposes only so not precise. Results are based on a Super35 camera sensor with a 50mm lens.
For more accurate depth of filed ranges, use this Depth of Field Calculator