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Photography Basics – Understanding the Exposure Triangle

Switching the camera mode dial from auto to any non-auto mode is a nice start, but to truly be a proficient photographer who must truly understand the exposure triangle.

The exposure triangle is simply the relationship between ISO, Shutter Speed and Aperture as they work together to create an actual exposure or photograph.  It is referred to as the exposure triangle because when you adjust one element, another element MUST change to capture the same exposure.  So when learning the photography basics and understanding the exposure triangle it is paramount to always remember this cause and effect relationship.

Before we get into the details and specific technical examples about understanding the exposure triangle lets first make sure we understand each of the elements – ISO, shutter speed and aperture.


  • ISO or ASA is a term from the film photography days which referred to film sensitivity to light.
  • The lower the film sensitivity or ISO the less “grainy” the photo would be. The same concept is true today with digital photography as ISO now refers to sensitivity of the camera sensor.
  • Just remember, the lower the ISO number the cleaner looking your photo will be – less “grain/noise”.   Note: at times high grain/noise can be used for artistic effect.
  • For a far more detailed discussion on ISO, check out this post: ISO Explained the Easy Way!

Tired of Grainy Photos? – You’ll love my brand new Crisp & Clean Presets Collection!

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Shutter Speed

  • Simply the amount of time, measured in seconds, that the camera’s shutter is help open allowing light to hit the sensor to make an exposure.
  • Example Shutter Speeds: 1/500, 1/250, 1/125, 1/60, 1/30, 1/15, 1/8, 1/4, 1/2 etc…


  • Aperture simply refers to how large or little the opening is thru the lens.
  • Aperture is what controls how much or little light can pass through the lens and onto the camera’s sensor.
  • Each lens has its own aperture range in terms of how wide and narrow of an aperture it can be set at. Aperture is measured in “f-stops” and a lower f-stop number such as 1.8 means a wider aperture (lets in more light), a high “f-stop” number like f22, means a narrower aperture, letting in far less light.
  • Aperture/f-stop numbers: f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22, f/32
  • Want to learn more about aperture?  Read this post: Fundamentals of Photography – Understanding Aperture

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Putting ISO, Shutter Speed and Aperture Together

The easiest way to think of how all 3 work together to give an exposure is to keep one of the three held constant – let’s make ISO constant to not worry about that changing as well. Remember that both aperture & shutter speed both control how much light is coming in thru the lens (aperture) and onto the cameras sensor (shutter speed), so if using a wider aperture (lower f-stop number) you are letting in more light and therefore your shutter speed should be faster compared to when using a narrower aperture (higher f-stop number) for the same given exposure.

For example, if you’re taking a photo and you’re using aperture priority mode, you set the camera lens to f/4 and the camera selects 1/250th as the appropriate shutter speed and you have ISO set at 200. If you decide to change the aperture to f/2.8 you are now letting in more light into the camera requiring an adjustment on shutter speed (faster) to let in the same amount of light between aperture and shutter speed. Since you are keeping ISO constant, the new shutter speed with aperture at f/2.8 from f/4 would be around 1/500th of a second.

Changing the aperture from f/4 to f/2.8 is letting in twice as much light, so in order to compensate for that extra light the camera is choosing a twice as fast shutter speed – 1/250th to 1/500th. Don’t worry though, in aperture priority mode, you just change the aperture and the camera’s light meter will determine the correct shutter speed.  To see why I love shooting in aperture priority mode over manual sometimes check out this read.

Key Takeaway – Understanding the Exposure Triangle

Always remember to think of “exposure” as simply the amount of light hitting the camera’s sensor or film. The sensor/film is being “exposed” to the light. We can control how much light hits the sensor by:

  1. Aperture – How LARGE of lens OPENING
  2. Shutter Speed – How LONG of a time the shutter remains open, to allow light in.
  3. ISO – How SENSITIVE to light the actual sensor is

Key tips to help you:

  • Always use the lowest ISO as possible for the cleanest (less grainy) images with the best dynamic range and color depth.
  • For faster shutter speeds use wider apertures and/or higher ISO
  • To prevent motion blur and get sharp photos, shutter speed should be at minimum 1 / (focal length) for full frame sensor cameras and 1/(1.5 x focal length) for crop sensor cameras. Note: rule above is rule of thumb for stationary subjects, moving subjects may require faster shutter speeds.

If you are a visual learner make sure to check out the video below to help improve your understanding of the exposure triangle!

Now it’s your turn!

I’d love to hear from you, what exposure element do you struggle with the most – understanding ISO, shutter speed or aperture?

Catch ya later,