Tips: depth of field
Sam Bailey is a freelance shooting producer/director who has worked on Coast, Countryfile and The One Show. He shares his tips for controlling depth of field on location, creating different effects such as soft interview backgrounds and a pull focus.
Depth of field relates to how much of your image is in focus at a certain distance from the camera. A shallow depth of field means only a small distance between your camera and what you’re filming is in focus. This means the background and foreground will be out of focus and blurry. This is an effect that draws the viewer’s eye to the subject.
This look can be referred to as a narrow or shallow depth of field but both mean the same thing.
We associate this look with bigger cameras with bigger lenses or with SLR stills cameras. Smaller video cameras can achieve a similar look if adjusted correctly.
Use of space
If you want to achieve a nice soft background whilst filming an interview, you should try to find a room with plenty of space to get some depth to your shot. This also gives you room to zoom in.
Zooming in on most video cameras gives you a narrower depth of field. Not something you can do very easily in a small space.
When you are playing with depth of field, using zoom, you want as much as you can get between your camera and your subject and the background.
Narrowing your depth of field using zoom is easiest on a tripod. It also cuts out the wobbles.
"Playing with depth of field is a chance to be a bit arty." – Sam Bailey
Beware that when filming interviews with a shallow depth of field, your focus becomes far more critical. When the interviewee leans forward, you can lose focus, so keep an eye on it and be a bit more attentive, checking and finding focus regularly.
The iris and ND filters
The iris which controls the amount of light you let into the camera is another way to help you achieve a shallow depth of field. The more you open the iris and lower the f stop number, the narrower the depth of field becomes, in this case defocusing the background.
ND or neutral density filters act like sunglasses for the camera. If you’re outside and it’s sunny enough for sunglasses, then the camera will need them too. Use ND filters if it is sunny, you are by the sea, you are on a sandy beach or you are working in the snow.
When you’re filming outside, to get more of a blurred, out of focus background and to really get that narrow depth of field, you want to whack in ND as much as you can. However, make sure you check your exposure is correct.
The use of a camera's macro mode can also help achieve a narrow depth of field. It is especially useful for focussing on objects close to the lens, whilst de-focussing the background.
Learning to control depth of field gives you the opportunity to film creatively. The more you can use light and colour, the more it will help the overall effect.