Depth of Field, Part 1:

How Aperture and ISO Affect Focus

Written and presented by Scott Ballard

Summary: Depth of field is defined by the range of distance where an image appears to be in focus. There are some key tools we have to adjust and control our depth of field, two of which are aperture and ISO. In this lesson we look at at how aperture and ISO affect depth of field.

Length: 3:22 minutes

Video Lesson

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An elementary part of the job of being behind the camera is making sure your subject is in focus. Focus within the frame is not only relative to how the viewer sees the subject or main action, but also the spatial relationship between subjects and objects within the frame.

The amount of focus a subject/object has between them and the world around them is referred to as Depth of Field. Depth of Field is an important storytelling tool for filmmakers. It can aid perspective, emotional resonance, action and understanding of a project. Depth of Field also determines when and how a camera operator adjusts their focus.

There are some key tools we have to adjust and control our Depth of Field: Chiefly: Aperture and ISO. The focal length of our lenses and filtration also aid in controlling our Depth of Field. Let’s look at lenses and aperture.

Depth of Field, Part 1: deep depth of field

In this lower light scenario we want to find focus both on the glass of wine and the actor as she reaches for the wine. However, as we focus from the wine to the actor we can see there is a discrepancy in the focus. We can either chose to set focus marks and rack focus from the glass to the actor, or we can increase our depth of field to minimize the difference in focus between the wine and the actor, drawing them into the same focal plane...

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Tools We Used

Depth of Field, Part 1: How Aperture and ISO Affect Focus
Five Questions to Ask When Choosing a Camera (Camera Lesson 13)
Four Types of Camera Systems (Camera Lesson 12)
Crew Positions: Who's Who in Camera Department (Camera Lesson 19)
Camera Exercise #2: The Best Fit Camera
Four Must Have Accessories (Camera Lesson 14)
Camera Exercise #3: Exposure Experimentation
Camera Exercise #4: Pulling Focus and Camera Routine
Staying Focused: Sharp Images (Camera Lesson 34)
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