Basic Video Production Tips - Depth of Field
One of the many, many ways a filmmaker can manipulate the look of an image is by understanding and controlling depth of field. Disclaimer: This blog post will not dig into the science and technical aspects about how camera sensors work; there are plenty of well-written video, photography and filmmaking essays out there about that. I’m more interested in simplifying, getting to the point, and sharing the experiences our video and camera crew goes through shooting on the field week in and week out during our video productions. Mind you, our video production company here in Vienna produces mostly corporate videos, interviews, testimonials, events and music videos. However all of the basic information mentioned is basically universal.
Quick and dirty, let’s get the basic concept out of the way; In a nutshell, three factors affect depth of field:
Aperture (f-stop) in Theory:
A small f-stop number (f/2.8 for example) will result in a shallow depth of field, in other words “less things” will be in focus, thereby giving you a softer back and/or foreground in relation to the subject being filmed. A higher number (say f/22) conversely gives the cameraman a deeper depth of field where much more shown on the frame is in focus.
Aperture (f-stop) in Practice
In these next two shots, our camera team had a testimonial style interview to set up in an upscale hotel room in Vienna, Austria. Both interviews were shot with the exact same lens (50mm) and same camera placement. Notice the huge difference in the background when the camera operator set the aperture to a lower or higher value. The decision on using a wider or narrower aperture when shooting anything ranging from interviews, testimonials, films or music videos depends on how the filmmaker wants to tell the story. Or in the specific case below, what our client preferred for their corporate video interview production ;)
50mm lens set to f/2.8 – Background completely blurred
50mm lens set to f/16 – Background in focus
50mm interview set-up
Focus Distance in Theory:
Simply put, the closer the cameraman places the subject to the camera in relation to the background, the shallower the depth of field becomes. In other words, give your subject some distance from the background and bring him/her closer to the camera if you're after a "blurry background"
Focus Distance in Practice:
The next two shots are from a crowdfunding campaign our video crew produced last year in Vienna. The screenshots are only a few seconds apart in the video. Notice how blurry the subjects in the background are on the first illustration since the cameraman composed the main subject closer to the camera.
Subject close to the camera
Subjects further from the camera
Focal Length in Theory:
Focal length is the third main factor that determines depth of field. The longer the lens (say 100mm, 200mm, 400mm) the shallower your depth of field will be. Wide-angle lenses on the other hand will give you a deeper depth of field. In other words, “more stuff” will be in focus.
Focal Length in Practice:
The next example was from another testimonial style corporate interview shoot in Vienna our video production team filmed earlier this year. Our video crew decided on a two-camera interview set-up this time. One camera had a 35mm lens on it, and the second camera a 100mm.
As you can see from the behind the scenes illustration below, the focus distance is basically the same (both camera operators have their cameras around the same distance from the subject). However this time the focal lengths were different, heavily affecting the shots’ depth of field. On the wider camera angle, the background is almost entirely in focus, which was an important factor for the testimonial shoot since the boxes had to remain legible in that shot.
Two-Camera Interview Set Up at Relatively Same Distances
35mm Lens – Deeper Depth of Field
100mm Lens – Shallower Depth of Field
When it comes to our company’s corporate video productions, we try our best to always allow our camera team or video crew to visit the filming locations weeks/days prior to shooting (location scouting). This saves so much time on the actual shooting day and avoids a lot of confusion between the client and the video production company.
For example: Need a medium-wide interview shot with an interesting-looking blurry background? Then make sure to ask for a big enough and nice-looking room/space that allows your camera team to put plenty of distance between your subject and the background in order for the cameraman to create some depth in the shot.
So many times we’ve gotten hired for corporate video shoots here in Vienna where the client wanted to film “beautiful” looking interviews and testimonials with creamy looking backgrounds, only to be shown a small, boring, white-walled office as their filming location option on the actual shooting day. That situation can be avoided with a simple location-scouting visit from the camera crew, producer, videographer or cameraman.
If all else fails and the locations have no depth whatsoever, throw your subjects in front of a long hallway ;)
Posted by Vitor Goncalves
Vitor is a filmmaker, cameraman and editor based in Vienna, Austria. He is the owner of Reel Arts Media.