The Basics of the Exposure Triangle

Exposure Triangle Feature Image

The Basics of the Exposure Triangle

Each element of the exposure triangle impacts the others; changes to one will require changes to the others. Exposure is the amount of light allowed to reach the camera sensor and sets the mood for the photo. High exposure creates a “light and airy” feel while low exposure creates a “dark and moody” feel. Since “proper” exposure can vary depending on personal preference, I will only cover the basics for understanding how to manipulate Aperture, Shutter Speed, and ISO to achieve your vision. Just know that overexposed means there is too much light and underexposed means there is not enough light.

 

Exposure Triangle

 

The Basics Of The Exposure Triangle

If your photos need more light, you can adjust the exposure in one or more of the following ways:

 

  • – Open your aperture. As I went over in Aperture Made Simple, this means reducing your f stop number
  • – Decrease shutter speed, as in a slower shutter speed
  • – Increase ISO

The opposite is true if you want less exposure:

 

  • - Smaller aperture
  • – Increase shutter speed, as in a faster shutter speed
  • – Decrease ISO

 

Informational Graphic showing the settings from the least light to the most light for the three elements of the exposure triangle - ISO, shutter speed, and aperture.

When you’ve decided on a shutter speed but the image is underexposed, then you can open the aperture and/or increase the ISO for more exposure. If the image is overexposed and you want less exposure, then use a narrow aperture or decrease the ISO.

 

Moonrise

If you’re set on your aperture instead, you could decrease your shutter speed and/or increase your ISO to get more exposure. Or increase shutter speed and decrease ISO for less exposure.

Since the biggest impact of ISO amount of digital noise in a photo, it’s best to set aperture and shutter speed first and then determine an appropriate ISO. If aperture and shutter speed are a priority, then your only option for more exposure is to increase the ISO. You can generally use a pretty high ISO before noise is noticeable, however, if you want a lower ISO, then you would need to decrease the shutter speed and/or open the aperture to increase exposure. If you do not wish to change two of the exposure settings, then the third is the only option for changing the exposure

 

Examples of Using The Exposure Triangle

 

Camping at Big Bend National Park at night.

In this photo, I set the aperture to f/22 for sharp landscape lines and the ISO to 100 for minimal noise.  The only option to get adequate exposure with these settings was to increase the shutter speed to 30 seconds. 

 

Conversely, I used a very fast shutter speed, 1/4000, and a fairly low f-stop, f/4, in this photo. Â To get enough exposure, I needed to increase my ISO 12800. If 12800 was too much noise, my first thought would have been to decrease the amount of time the shutter is open.

There is no hard and fast rule on how to choose the exposure settings for a particular scene. If you see that an image is over or underexposed, look at your settings to see what you can tweak. If you don’t like the exposure and don’t want to adjust the shutter speed, there are a variety of ways to manipulate ISO and aperture to adjust the exposure.

 

Test Yourself

The photo below is overexposed, what could I have changed to get better exposure?

Camera Settings:

ISO: 100

Shutter Speed: 1/125

Aperture: f/5.6

 

Test yourself example for improving your knowledge of the exposure triangle.

 

Answer

Answer: Increase shutter speed, as in use a faster shutter speed.

Explanation: ISO was already as low as it could go and the aperture wasn’t that high.  But the shutter speed could have been much faster.

 


 

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