Aperture Made Simple


Aperture controls the depth of field and is arguably the most important element of the (exposure triangle ISO, shutter speed, and aperture). The size of the aperture will impact the settings needed for ISO and shutter speed to get proper exposure.

Exposure Triangle

What is aperture?

Aperture is the size of the opening in the lens controlling the amount of light reaching the sensor. A large aperture is a wider opening and allows more light to reach the sensor. A small aperture is a more narrow opening which allows less light to reach the sensor.

Aperture Graphic

Think of aperture as the pupil of your eye. Do you ever turn the light on first thing in the morning and it’s painfully bright for a second? 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 took a second to widen and allow more light so you can see.

Simply Put:

  • Large aperture = more light
    • If using manual mode, you’ll want to use a faster shutter speed and/or a smaller ISO.

  • Low aperture = less light
    • If using manual mode, you’ll want to use a slower shutter speed and/or a higher ISO.

How Do I Use Aperture?

A large aperture (small f-stop number) isolates your subject by blurring the background and/or foreground. 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 is blurry? That’s because they enlarged your pupil.

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

A small aperture (large f-stop) makes the foreground, middle, and background sharp. This is ideal for landscape, architecture, and creating sun-glare.

In this photo, I used a large aperture (f/11) so the whole 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 aperture than an f/16. This may seem to be the opposite of what makes sense – in short, the f-stop number is actually a fraction. If you’re interested in understanding the numbers in detail, check out PhotographyLife’s blog on aperture. Otherwise, just remember that f-stop numbers are the opposite of aperture size.

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

Autumn Leaves Falling

Small, f/3.5

Père Lachaise Cemetery in Paris, France

Large, f/11


Aperture Pin

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