How Do Object Distance and Focal Length Affect Depth of Field?

Note: this is Part 2 of a series on depth of field. Click here for part 1, which explains the relationship between aperture size and depth of field.)

Besides using aperture size, photographers can also control depth of field by changing the camera-to-object distance or the lens focal length. Specifically:

  • For a fixed focal length and aperture size, increasing the object distance will increase the depth of field.
  • For a fixed object distance and aperture size, increasing the focal length will decrease the depth of field.

These two effects are closely related, and the quest to understand them offers a great example of how we can use equations to augment our intuition while solving relatively complicated problems. Read on if you want to learn more!

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