What Is 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, is tough.

This exposure triangle is simply the relationship between three elements: aperture, shutter speed, and ISO. These three components 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.

When learning the photography basics and understanding 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, let’s first make sure we understand the three sides of the exposure triangle: aperture, shutter speed, and ISO.

Side 1: ISO

ISO refers to the sensitivity of the camera. A high ISO means there’s more sensitivity, while a low ISO means the sensor becomes less sensitive to the amount of light.

If you set the ISO too high, you might get a very bright image that has lots of visible dots. Auto ISO creates a balanced exposure depending on the aperture, shutter, and camera settings. For a far more detailed discussion on ISO, check out this post: ISO Explained the Easy Way!

Set the Right ISO to Avoid Grain

Picking the right ISO settings will be different for every image. Increasing the ISO enables photographers to shoot with less light. However, this results in increased noise, and subsequently, less detail. 

The lower the film sensitivity to light the less “grainy” the image will be. The same concept is true today with digital photography, as ISO now refers to the sensitivity of the camera sensor.

Just remember, the lower the number, the cleaner looking your image will be. This means there will be less “grain/noise.”   

However, keep in mind that sometimes photographers use high grain/noise as an artistic effect.

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exposure triangle

Side 2: Shutter Speed?

This exposure triangle concept is simply the amount of exposure time (measured in seconds) that the camera’s shutter is open allowing light to hit the sensor to make an exposure. The higher the number, the fast the shutter will open and close.

Slower speeds give a long exposure time for the sensor to collect light and produce a higher exposure. Meanwhile, a faster one means less exposure time for the sensor to receive the amount of light, resulting in lower exposure value. In short, this exposure triangle concept determines whether the motion appears blurred or frozen.

Examples: 1/500, 1/250, 1/125, 1/60, 1/30, 1/15, 1/8, 1/4, 1/2 etc…

Most cameras have a built-in 30-second time limit for the shutter to open. For long exposure, set the camera into Bulb mode, which lets you use an external remote control to trigger the shutter button. In effect, you can manually control how long the shutter opens.

How Shutter Speed Relates to Motion Blur

Shutter speed determines the amount of light the camera sensor receives. Combining this exposure can either blur or freeze motion. 

If you are into sports, you will want a fast speed to freeze motion in images. If you want a dramatic blur for your street photos, you’ll need to work at a slow speed. 

Try to practice shooting a photo with slower speeds while using lower ISOs (like ISO 100 or 200) for more detail. At ISO 100 or ISO 200, the sensor is at its least in sensitivity to light. Another option is to use a slow speed with a narrow aperture. 

Side 3: Aperture?

This exposure triangle concept refers to how large or small the opening is thru the lens, as you can see in the above illustration.

This opening is what controls how much or little light can pass through the camera lens and onto the camera’s sensor.

The depth of field is a byproduct of this concept. Wider apertures produce a shallow depth of field, which isolates the subject from the background. Narrower apertures result in a greater depth of field, letting more details in images to be in focus.

Each lens has its own range. This means one lens can open as wide as f/1.4, while others start at f/4.0. 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 much less light.

Aperture numbers: f/1.4, f/2, 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

exposure triangle

How Does the Exposure Triangle Work?

The easiest way photographers think of how all three exposure triangle elements work together is to keep one of the three exposure triangle components constant. Let’s make ISO the constant (so don’t worry about that changing). The next step is to choose your aperture.

Remember that both aperture and shutter speed both control the amount coming through the lens (aperture) and onto the camera’s sensor.

Therefore, if using a wider aperture (lower number) you are letting in more light and therefore your speed should be faster compared to when using a narrower aperture (higher number) for the same given exposure.

ISO impacts noise; aperture manages depth of field; while speed controls motion. As speed increases, blur decreases. Hence, use a slow speed if you want to blur the movement. Opt for a faster speed if you need to freeze movement.

The depth of field decreases as the aperture size increases. Choose a smaller aperture to keep the background in focus, while a larger aperture will keep the background blurry. 

As the ISO increases, digital noise also increases. Set the camera to the lowest ISO possible for a clearer image. If you want to create digital noise, boost the ISO. 

Exposure Triangle Examples

Based on the light outdoors, you set your ISO at 200. If you’re taking an image and you’re using aperture priority mode instead of shutter priority, you set the camera lens to f/4, and the camera selects 1/250th as the appropriate shutter speed.

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 an 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 the amount of 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.

Another example: let’s say that you want to take a shot of a bird in flight. In that case, the first setting you’ll want to adjust is the shutter speed, to make sure you freeze the motion and then adjust aperture and ISO accordingly.

You can start with a shutter speed of at least 1/1600 of a second, but depending on the bird you’re photographing, you’ll need a faster shutter speed.

If you want to focus on the bird’s eye or head, you can try setting a mid-range aperture like f/5.6 or f/8. Once you feel more comfortable adjusting this setting, you can try using wider apertures like f/4 or f/2.8.

Finally. focus on dialing in your ISO. If you are shooting in the middle of the day with bright sun, your ISO might be around 400. If you’re shooting during sunrise or sunset, your ISO setting might be closer to 1600.

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 adjusting these elements:

  • Aperture – How LARGE of lens OPENING
  • Shutter Speed – How LONG of time the shutter is open, to allow more o less light in.
  • ISO – How SENSITIVE to light the actual sensor is

A few key exposure triangle tips to help you:

  • Always use the lowest ISO as possible in your image! That way, you can try to achieve the cleanest (less grainy) image with the best dynamic range and color depth. Outdoor, this will range from 100-400, Indoors ~ISO400-3200, Dark Receptions ISO 1600+. Please note that this exposure value will vary slightly. How much this exposure value change will depend on the ambient light in the situation.
  • For faster speeds (to capture movement), use wider apertures and/or high ISO.
  • To prevent blur and get a sharp image, the shutter speed should be at minimum 1 / (double your lens focal length) for full-frame digital sensor cameras and 1/(1.5 x focal length) for crop sensor cameras. Note: this is the rule of thumb for stationary subjects, moving subjects may require faster shutter speeds.

If you are a visual learner make sure to check out this video! This will help improve your knowledge of the exposure triangle: aperture, shutter speed, and ISO! Please let me know in the comments if there is anything I can explain further, or doesn’t make sense! I’m here to help you understand the exposure triangle!

Now it’s your turn!

I’d love to hear from you! What exposure triangle element do you struggle with the most? How will you practice setting aperture, shutter speed, and ISO? Understanding ISO, shutter speed, or aperture? What mode do you prefer? Hit me with all your exposure triangle questions!

Catch ya later,
Cole