Do you love that cinematic shallow depth of field in portraiture? The relationship between aperture and depth of field is one of the first things to understand in photography. We’re going to show you how to use the lens’s aperture to control the depth of field in less than 60 seconds.

Video – How to Create Depth of Field with Aperture

Review – What is Aperture?

Aperture refers to the diameter of the opening that allows for light to enter the lens and hit the camera sensor. Aperture size is measured in focal ratios and denoted as f/numbers. The simplest way to understand aperture size is:

  • Wide aperture = lower f/number
  • Narrow aperture = higher f/number

Because apertures are measured fractionally, the wider the aperture the lower the f/number (f/2). The narrower the aperture, the higher the f/number (f/22).

Aperture and Depth of Field

Depth of field in an image correlates to the size of the aperture. An easy way to remember this is, the lower your f-number, the shallower your depth of field. Likewise, the higher your f-number, the deeper your depth of field.

  • Wide aperture = f/2 = shallow/smaller depth of field
  • Narrow aperture = f/22 = deeper/larger depth of field

Typical kit lenses don’t offer wide apertures. But, simple inexpensive (varying from $100 to $2000) 50mm prime lenses is a wonderful first addition in your kit to achieve a cinematic shallow depth of field in portraiture: Canon, Nikon, and Sigma.

F-Stops and Exposure

Not only does the size of your aperture control your depth of field, but also the exposure.

  • Wide aperture = f/2 = more light and brighter exposure
  • Narrow aperture = f/22 = less light and darker exposure

Understanding aperture is one of the keys to mastering Manual exposure. Learn more about the Exposure Triangle from Photography 101 here:


We hope this article helps you understand the relationship between aperture and depth of field.  If you enjoyed this education and you want to learn more, master manual mode and the basics of photography in the Photography 101 Workshop. Upgrade to SLR Lounge Premium for unlimited streaming to a collection of photography education, ranging from technical to lighting to post-processing and more!