DSLR Camera Basics

Depth of Field

Depth of field is the distance that appears to be in focus in front of and behind the point on which the lens is actually focused. Depth of field is determined by aperture, lens focal length, and the distance to the subject:

  • Aperture: Wider apertures (lower f-numbers) reduce depth of field, smaller apertures (higher f-numbers) increase depth of field.
  • Lens focal length: Longer focal lengths reduce depth of field, shorter focal lengths increase depth of field.
  • Distance to the subject: Shorter distances reduce depth of field, greater distances increase depth of field.
Short depth of field
Long depth of field
Wide (low f-number)
Small (high f-number)
Focal length
Long (telephoto lens)
Short (wide-angle lens)
Distance to subject

Depth of field

Depth of field: short
Wide aperture
Long focal length
Short distance to subject
Depth of field: long
Small aperture
Short focal length
Long distance to subject

Although the above photographs were taken in the same location, background details are much more blurred in one than in the other. As you can see, you can change the impression the photograph creates by changing the aperture, focal length, and distance to the subject.