Aperture Made Simple

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All photos are original to the author unless otherwise noted. 

Aperture controls the depth of field and is arguably the most important element of the exposure triangle, which also includes ISO and shutter speed. Aperture is one of the three elements that contribute to exposure and will influence the settings needed for ISO and shutter speed.

Table of Contents

Exposure Triangle Infographic Shows How ISO, Shutter Speed, and Aperture Work Together

Aperture refers to the size of the shutter opening, which controls the amount of light that reaches sensor. A large aperture has a wider opening and allows more light to reach the sensor, while a small aperture is more narrow and allows less light to reach the sensor.

What is Aperture

Understanding Aperture Size

How Aperture Contributes To The Exposure Triangle

Which Aperture Should I Use

The Best Cameras For Large Apertures

Aperture Infographic explaining how much light narrow and wide apertures let into the camera sensor

Your eye works in the same way; do you ever turn the light on first thing in the morning and it’s painfully bright for a moment? In that split second it takes to adjust, your pupils are changing from a large diameter to a small diameter to let in less light. The opposite is true when you turn off the lights at night and it takes a second before you can see where you are going. When you turned off the lights, your pupils need to widen to allow in more light so you can see.

Simply Put:

  • Wide aperture = more light
    • If using manual mode, you’ll want to use a faster shutter speed and/or a smaller ISO if your images are overexposed.
  • Small aperture = less light

    • If using manual mode, you’ll want to use a slower shutter speed and/or a higher ISO if your images are underexposed.

How Do I Use Aperture?

A large aperture (small f-stop number) isolates your subject by creating a blurry background and/or foreground; often referred to as bokeh. A large aperture is ideal for macro photography, portraits, blurring out distracting backgrounds, and low-light situations. Back to the pupil analogy; have you ever gotten your eyes dilated at the eye doctor and everything was blurry? That’s because they enlarged your pupil.

In this image, I used a large aperture (f/2.0) to achieve the blurred background

Rain Drops on a Sprenger's Tulip
Arlington National Cemetery in Spring

A small aperture (large f-stop) makes the entire image sharp and is ideal for landscape photography, architecture, and creating sun-glare.

In this photo, I used a large aperture (f/11) so the entire scene is sharp

What Is F-stop And How Does It Pertain To Aperture?

The f-stop number is the numerical representation of aperture. The lower the f-stop number, the larger aperture. f/1.8  is a much larger than f/16 which may seem counterintuitive, but it’s because the f-stop is actually a fraction. If you’re interested in understanding the details, check out Photography Life’s blog on aperture. Otherwise, just remember that f-stop numbers are the opposite of aperture size.

Understanding Aperture On Camera Lens

If you are feeling frustrated because you can’t seem to get that beautiful background blur, it could be because the lens’ maximum aperture isn’t wide enough. All lenses list the aperture on the side or the end and will look like something like 1:2.8 or 1:2.8-3.5. In this example the aperture is on the bottom right and ranges from f/3.5 to f/6.3. 

Many zoom lenses have a variable aperture which means the maximum aperture decreases as the focal length increases. 

Good Lenses For A Wide Aperture

Practice Using Aperture Priority Mode

Aperture priority mode is a camera setting where the photographer has creative control over the aperture settings while the camera automatically sets the ISO speed and shutter speed. Use this mode to explore how changing the aperture size impacts the image blur and shutter speed. Note how the camera selects a faster shutter speed to limit the amount of light to reach the sensor when you select a wide open aperture.

Test Yourself!

See if you can guess the size of the aperture used (small or large), bonus points if you can guess the actual f-stop. Put your answers in the comments!

Answers listed under each picture.

Peregrine Falcon
Small, f/2.8
Sunset in White Sands National Park -  Las Cruces, New Mexico
Large, f/11
Large, f/11
Orange Leaves Lost Maples State Park
Small, f/2.8

Author Bio

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Delaney is a Business Analyst by day and a travel and wildlife photographer by night who is using her skills for translating complex technical language into easy to understand concepts to make photography achievable at all skill levels. You have questions; she has answers.

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