Depth of Field, Part 4:
Using a DOF Calculator + Advanced Tips and Tricks
Presented by Scott Ballard
Written by Tim Park and Scott Ballard
Summary: When working depth of field, it is almost a requirement to use a depth of field calculator. This allows a cinematographer to not only better plan shots, but empowers him or her to actually move the depth of field around to exactly where the project needs it to fall.
In this lesson we go through the steps of using a depth of field calculator, as well as a list of advanced tips and tricks to push it around your set.
Note: For this lesson we used the Digital DoF iPhone app by Indie Film Gear, LLC. When running calculations online, we used PhotoPills Depth of Field Calculator. These may not be the best for your needs, they are just what we use since they get the job done. You may notice that calculations are slightly different depending on which calculator you use. We will discuss why in the next lesson, Depth of Field, Part 5. (We are not affiliated with either company and received nothing from them for using their calculators in the lesson.)
Length: 8:08 minutes
Now that we have the basics of DOF from our previous lessons, let me show you some ways you can push your DOF around so you have better control of it. In order to do this, let me first teach you how to use a very handy piece of technology known as the DOF Calculator.
There are several DOF calculators on the market — both as online and as smartphone apps — and most do about the same job. They do the heavy lifting of calculating your DOF range and hyperfocal distance based on your shooting conditions: sensor size, focal length, f-stop and subject distance. DOF calculators are a must have tool, both on-set and when planning your shots. Let’s go through the steps of inputting your camera settings.
There are some preliminary considerations before beginning. The first step is determining your camera’s specific sensor size, such as if it’s a cropped or Micro 4/3 sensor or a full 35mm sensor. Most apps make this easy by letting you just pick the camera model. With this app, I am able to specifically choose which camera we’re using. We shot this DOF series on a Sony A7S, so I’m going to input that into my app.
Once that is set, I can begin. I know I want to use my 50mm lens, so I set the focal length to 50. Next, I know my, aperture will be f/16, so I set the f-stop accordingly. Now I can frame up my subject. By running a tape measure from my camera’s focal plane marker to the subject, I see that my subject is exactly 12 feet away. With this calculation, I have a DOF range of 31’ 6”. That means that there is range of 31’ 6” that my subject can move around in and remain in focus, along with the objects surrounding my subject.
Something to notice is that the calculator shows this range is not split 50/50, meaning this range is not 15’ 9” in front and 15’ 9” behind the subject. Rather, that we have 4’ 11” in front of the subject and 26’ 7” beyond the subject that will be in focus. That means it is more of a 16/84 split, with most of the DOF behind our subject.
Now let’s play around a little with the settings...
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Camera / Audio
- Sony Alpha a7S Mirrorless Digital Camera
- Rokinon Cine DS 6 Lens Kit with Sony E Mount
- Bright Tangerine Misfit Matte Box
- TruND Neutral Density Filters (4″x5.65″): 0.3, 0.6, 0.9, 1.2, 1.5
- Tilta FF-T03 15mm Follow Focus with Hard Stops
- Sachtler Panorama 7+7 Head 100mm (similar head: 1006 DV 10 SB Fluid Head)
- Sachtler Carbon Fiber Tripod (similar tripod: Carbon Fiber HD Tripod Legs)
- Movcam Cage for Sony A7S
- Wooden Camera A/B Gold-Mount Plate for Sony A7, A7r and A7s
- Audio Technica AT835b Shotgun Microphone (similar microphone: Audio Technica BP4071 Shotgun Microphone)
- Wooden Camera DSLR A-Box
- Delkin Devices 64GB SDXC Memory Card 600x UHS-I
- DSC Labs One Shot Reference Chart (Matte Finish)