Understanding Depth of Field - Laura Beth Love DP
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Copyright © Laura Beth Love and LBLove.com and Tough Love Fit Blog. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Laura Beth Love and LBLove.com or Tough Love Fit Blog, as appropriate, with appropriate and specific direction to the original content.

Depth of Field – Made Simple

Depth of Field – Made Simple

What is Depth of Field?

 

Depth of Field is a calculated, range of distance, wherein objects will appear to be in acceptable focus.

Basically, it tells you how much stuff in front of your camera will be in focus at one time.  If an entire football field is in focus, you would say that you have very deep depth of field; if the actress leans forward two inches and is suddenly out of focus, then you would say that you have very shallow depth of field.  You will often see it written as an acronym: “DOF.”

Why is Depth of Field Important?

DOF is one of the most essential tools that you have as a filmmaker.

Focus may seem very clinical: a shot is either in focus or it’s not; right or wrong.  But as soon as you can take that for granted, (i.e. your camera assistant is a professional) you get to wield focus as a tool to guide the audience’s eye.  (Read 5 Tips For Better Focus)

Depth of field helps you tell the audience where to look!

RC_macro Shallow Depth of Field, “Rice Counter, Ice Sleeper”

Deep Depth of Field, "Rice Counter, Ice Sleeper" Deep Depth of Field, “Rice Counter, Ice Sleeper”

DOF and the Audience

Deep Depth of Field on "Tabloid Vivant" Deep Depth of Field on “Tabloid Vivant”

Deep depth of field tells the audience, “look at everything, everything is important.”

Shallow depth of field tells the audience, “look here, this is what is important.”

Once you control where they are looking, then you can shift their gaze as you shift focus to different planes within the frame, “Look here!  Now, look here!”

 (DOF is one of many tools we have to guide the eye our audience.)

Depth of field should support the drama of your story, but, without proper understanding, it can also work against you.

For example, in a scene with several characters, or big action, (e.g. stunts or a dance number), if your DOF can’t hold all of the important action in acceptable focus, it could be distracting and frustrating for the audience.

As a director and the cinematographer, you must understand DOF so that your blocking of camera and actors, lens choices, and lighting levels will all correspond, and compliment each other, to achieve the story you want to tell!

How Do I Calculate DOF?

The short answer? Just look it up.  The “calculations” are already done for us.  Find a DOF chart, or download a DOF App for your smart phone or computer.  Enter the data into the app (or cross reference the data, if you are looking at a chart)!

DOF Cartoon - Laura Beth Love, DP

There are 4 factors that affect Depth of Field:

    1. Format -What size sensor does your camera have?  What resolution setting will you choose?
      These factors change your field of view, which affects depth of field in two ways:
      Indirectly, by affecting your choice of focal length, and directly, by determining your circle of confusion.

      A small sensor has a narrow field of view, which means you will generally end up using wider lenses than you would on a larger sensor.  For this reason, cameras with smaller sensors (e.g. 1/3″ or 2/3″) are said to have deeper depth of field than camera with large sensors.

      Your format is usually decided before you start shooting and doesn’t change. (If you do change your sensor size or resolution, just remember to update your DOF calculator)

       

    2. T-stop This is your shooting stop (iris setting),
      A smaller number will give you more shallow DOF (e.g. T1.4).
      A larger number will give you deeper DOF (e.g. T16).

 

  • Focal LengthWhat lens have you chosen?
    A long focal length (narrow) lens will give you a more shallow DOF.  A short focal length (wide) lens will give you deeper DOF.
    The focal length is used to name each prime lens (ie. a 50mm lens).
    A zoom lens has variable focal lengths.

 

 

  • Focal Distance – This is the distance between the focal plane  (on your camera) and your subject.  A short distance will create more shallow DOF, longer distances will give you deeper DOF.

 

Practical Application

You should consider depth of field with every shot that you design or setup, just as frequently as you consider exposure or composition.  Exploring depth of field in your free time (with a DSLR, or even your camera phone) will help you become more practiced and more confident in wielding this tool on set.  Eventually, all of this terminology, and the meaning of it all, will be second nature.

Simple?  This Still Looks Complicated!

I find these technical aspects of cinematography to be kind of like a 3D math puzzle.  It can be intimidating at first, but with practice you can become a master!

The best way to begin internalizing all of this is simply to shoot as often as you can, with any camera, and analyze what you see.

When you understand DOF, you’ll be subconsciously considering it every time you design a shot or block a scene.  As a director, you’ll reference DOF when first describing what you want to the DP.  As a DP, you’ll be considering DOF as you interpret what the director is describing to you.

All of the steps outlined above will start to happen instantaneously, to the point where you might not even wonder any of that aloud.  You’ll just know to say “75mm, right here” or the DP will tell the gaffer “we’re going to need this scene to be at a T5.6.”

As a camera assistant, you’ll be thinking about DOF as you listen to the director and DP talk through the scene.  You will get in the habit of calculating DOF as soon as you’ve set up the camera and lens, and have been given an expected shooting stop (T-stop).  There are a number of ways understanding DOF is specifically useful to the 1st AC (focus puller).  I’ll outline those in another post.

Also, for producers, directors, predators, one-man-bands, and camera assistants: here are 5 tips to have sharper focus on set!

Best of luck!  And let me know how it goes!  Subscribe to this blog for email updates!

 

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Copyright© Laura Beth Love and LBLove.com, 2015. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Laura Beth Love and LBLove.com, as appropriate, with appropriate and specific direction to the original content.

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