Exposure Triangle Photography Guide

The exposure triangle is an essential tool for selecting the correct combination of camera settings, consisting of shutter speedf-stop (controls aperture), and ISO, for any shooting situation.

Shutter Speed, F-Stop & ISO each represent a point on the exposure triangle.

Each noted setting also controls image brightness & visual image attributes such as motion blurdepth of field, & image noise.

Below, you’ll learn step by step methods for selecting the correct camera settings, for any shooting scenario, mastering the exposure triangle.

Table of Contents

Exposure Triangle Camera Technique Videos

The following videos teach my shooting workflow for selecting the correct exposure, shutter speed, f-stop, ISO, and histogram.

They were created to supplement the writing contained, below, on this page.

Click & Access the rest of my Landscape Photography Journals Videos. 

The 4 Factors Controlling the Exposure Triangle

This page requires a prior understanding of each setting, f-stop (controls aperture)shutter speed, & ISO, used to control the exposure triangle. 

Every photograph is controlled by 4 specific factors, each as important as the next.

The photography exposure triangle provides a methodical, step by step logic. This allows the photographer to evaluate each of the 4 factors, for any shooting scenario, thus determining the correct camera settings, producing the optimal image.

The 4 factors are as follows:

  1. Scene Luminance (Light Intensity): The amount of light available in the scene being photographed. Luminance is an absolute value measured in candela per square meter (cd/m^2). For example, sunny bright days have high scene luminance and dark scenes like twilight have low scene luminance.
    • Luminance is the only factor the outdoor photographer can’t control. The remaining three are controlled via the following camera settings:
  2. F-Stop: Controls aperture diameter, thus the amount of light passing through the lens which is then collected by the camera sensor.
  3. Shutter Speed:  Determines the amount of time the camera sensor is exposed to light from the scene.
  4. ISOISO determines the in-camera amplification of light information (signal) produced by a specific scene luminance, f-stop, and shutter speed.
    • ISO DOES NOT change the sensitivity of the image sensor, EVER.

The 2 Requirements of Successful Photographs

Every successful photograph has 2 fundamental requirements, each dependent of the 4 factors above.

These two requirements provide a “road map” allowing you to create beautiful images and improve your photography on a consistent basis.

Requirement 1: Exposure / Image Brightness

This is a physical requirement that ensures a picture displays the correct color & lighting. 

Using the correct camera settings, a combination of shutter speed, f-stop, & ISO, the brightness of the image produced will match that of the scene being photographed, creating the optimal exposure.

The incorrect camera settings produce underexposure or overexposure, which are simply defined as follows, and technically defined further down the page:

  • A photograph is underexposed when it’s darker than the scene being photographed.
  • A photograph is overexposed when it’s brighter than the scene being photographed.

Example Images – Under & Overexposed

Technical Note: All pictures on this page are unedited RAW image files compressed to JPEG format for online viewing. Always use RAW image format for the highest image quality. 

Slide Left – Overexposed || Slide Right – Underexposed

The following image shows the correct exposure for the scene, capturing the maximum amount of highlight & shadow detail in a single exposure.

Twilight in the Andes Mountain Range – Patagonia, Chile

Using a RAW image processor, such as Lightroom or Camera RAW, the dark details can be recovered from this exposure, matching it to the actual scene.

If the incorrect exposure triangle settings are selected, the RAW file will collect incorrect color & tonal information about the scene.

Below, you’ll learn to select the correct exposure triangle settings producing the optimal exposure for any scene.

Requirement 2: Visual Image Attributes 

This is a creative requirement that allows the photographer to produce the desired mood, feeling, or visual image attribute within a photograph. 

Prior to taking every picture, the photographer has a mental image of the pictures final outcome. The mental image may consist of one or many image attributes.

An image attribute is a specific visual effect obtained from varying camera settings such as f-stop, ISO & shutter speed.

After learning the image attributes (shown below) produced by each setting, the photographer starts to visualize what a photograph of a scene could look like, instead of seeing what’s actually there in the present moment.

The photographer’s goal is turning the creative mental picture, containing their desired image attributes, into a digital photograph that matches.

Shutter Speed Image Attributes

Shutter speed controls the amount of motion blur produced by moving objects within a composition.

  • Longer shutter speeds produce more motion blur.
  • Shorter shutter speeds produce less motion blur.

Reference the Shutter Speed Photography Guide for complete details & discussion.

Slide Left – 5 s. Shutter Speed, More Motion Blur || Slide Right – 1/30th s. Shutter Speed, Less Motion Blur

ISO Image Attributes

Zooming in and magnifying the example above (shown below) it’s possible to see the effects of low ISO vs. high ISO on image quality.

The image with less motion blur was photographed at a high ISO value of 1600. The image with more motion blur was photographed at a low ISO value of 100.

The ISO1600 image is very noisy. The colors and details become distorted by the image noise, significantly reducing color quality, detail, and sharpness.

The ISO100 image contains sharp detail and vivid color with no noise.

  • Increasing ISO increases image noise & decreases image quality.
  • Decreasing ISO decreases image noise & increases image quality.

Reference the ISO Photography Guide for complete details & discussion.

Slide Left – Low ISO, No Noise || Slide Right – High ISO, Increased Noise

F-Stop Image Attributes

F-stop, also known as f-number or f-stop value, controls the lens aperture diameter and depth of field (focus range).

  • Increasing f-stop increases depth of field and decreases aperture diameter.
  • Decreasing f-stop decreases depth of field and increases aperture diameter.

For example, changing from f/2 to f/16 would be increasing the f-stop value. Changing from f/11 to f/8 would be decreasing the f-stop value.

A photograph of rocks on a beach allows you to easily see the changes in depth of field due to changes in f-stop value.

Reference the Aperture & Depth of Field Photography Guide for complete details & discussion.

Slide Left – f/16, Large Depth of Field || Slide Right – f/2.8, Small Depth of Field

Section Review

Each photograph is controlled by 4 specific factors, scene luminance, f-stop, shutter speed, and ISO.

Nature controls scene luminance and the photographer controls f-stop, shutter speed & ISO.

Each successful photograph has 2 requirements each dependent of the 4 factors above.

  • The first requirement determines the exposure or image brightness.
  • The second requirement determines the photographer’s desired image attributes which specify the final outcome of the digital image.

Each of these basics provides a foundation for learning the photography exposure triangle, as discussed in the following sections.

Exposure Stops – Shutter Speed, F-Stop & ISO

This topic is covered thoroughly for each setting, F-Stop, Shutter Speed and ISO in their respective in-depth guides, linked at the top of this page.

We will  quickly review it in this section.  You should already have a good idea of how exposure stops work, prior to moving on.

Click & download the exposure triangle PDF for reference during the following sections.

Chart Disclaimer: The chart is used to compare changes in individual camera settings to the correlating change in light, measured in stops or Relative Exposure Value (+/-EV).

The chart does not compare one specific camera setting to another. The fact that specific settings line up is arbitrary.

An exposure stop or stop for short, provides a universal scale to measure the increase and decrease in light, exposed to the image sensor, due to changes in shutter speed & f-stop.

For ISO, exposure stops provide the increase or decrease in signal (light information) amplification, thus how much light is required to produce the optimal exposure.

Overall, stops provide an easy way for the photographer to increase or decrease image brightness or adjust f-stop, ISO, and shutter speed settings, controlling specific image attributes.

Quick Reference F-Stop & Shutter Speed:

  • An increase of 1 stop for f-stop or shutter speed doubles the amount of light exposed to the image sensor, providing a brighter exposure.
  • A decrease of 1 stop reduces the amount of light information collected by half, providing a darker exposure.

Quick Reference ISO Settings:

  • An increase or decrease of 1 stop in ISO does not affect the amount of light exposed to the image sensor.
  • 1 stop increase in ISO amplifies the signal by 2, increasing image noise and brightness.
  • 1 stop decrease cuts the amplification in half, decreasing image noise and brightness.

Exposure Value (EV) Basics

Digital cameras have a built in “reflected light meter” which approximates the scene luminance produced by a given composition.

This is the camera’s way of “knowing” how much light is coming from a specific scene. For example, are you photographing a bright sunny day or stars during twilight?

This process is known as metering and can also be called, camera metering or exposure metering.

Metering does not depend on the current camera settings of f-stop, ISO, and shutter speed. Metering only depends on the amount of light in a given scene/composition.

  • Camera meters make educated guesses at scene luminance using sensors and algorithms.
  • These approximations are not perfect.
  • It’s the photographer’s job to correct for any small errors in the approximations, as taught below.

Let’s call the camera metered amount of scene luminance, for a given composition, Scene Light Value (Scene LV). 

Scene Light Value approximates the scene luminance for a given composition and assigns it a number, depending on the how much light is present.

The larger the Scene LV the brighter the scene being metered.

Reference – Common Scene Light Values for Landscapes

These values are just approximations for a frame of reference. In most situations, they prove to be very accurate.

In the following section, you’ll learn to integrate them with real world shooting scenarios.

The scenes below start with the highest scene luminance (brightest) and end with the lowest (darkest).

Bright Sunny Day, Direct Sunlight: 16

Clear Blue Sky: 15

Just Before Sunset: 12 to 14

Sunset: 11-13

Just After Sunset: 8 to 11

Twilight: 2 to 8

Moon lit landscapes (Dependent of Moon Phase): -2 to 5

Aurora / Northern Lights: -6 to -3

Milky Way & Night Sky: -11 to -7

Now that the camera has metered the scene and determined it’s brightness, we will select the correct camera settings to match, producing the optimal exposure.

Absolute Exposure Value

Absolute Exposure Value (EV) is a rating system which allows the photographer to compare the “light capturing potential” of one combination of f-stop and shutter speed compared to another, at ISO100.

Absolute Exposure Value is calculated using the following equation.

This is all calculated automatically by your camera.

To understand exposure and select the correct settings, you need to understand how it works! I’ve also provided a chart below for quick reference.

EV = log2 ((f-stop value^2) / shutter speed)

Technical Note: log2 denotes log base 2. Numerical results are rounded to the closest stop. 

Example Calculations & Discussion

Our goal is to select the correct camera settings, producing an EV that matches the scene light value above, for the scene we are currently photographing.

  • Matching the Absolute Exposure Value to the Common Scene Light Values for Landscapesabove, the photographer can easily determine if these specific settings will produce the correct exposure, for the current amount of scene lighting.
  • EV does not determine if specific settings produce the photographer’s desired Visual Image Attributes. It’s only a quick reference for the amount of light specific settings can “collect” from a scene.

Remember, this is all done automatically by your camera.

Here are some examples…

Settings: f/8, 1 second, ISO100

EV = Log2((8^2)/1) = 6.

This EV falls in the range of 2-8. This combination of settings would probably produce the correct exposure for early twilight, as noted in, Reference – Common Scene Light Values for Landscapes, above.

Settings: f/5.6, 2 second, ISO100

EV = Log2((5.6^2)/2) = 4.

This EV also falls in the range of 2-8. Compared to the setting above, this EV is less, so it would produce the optimal exposure during a darker part of twilight.

Settings: f/1, 20 second, ISO100

EV = Log2((1^2)/20) = -4.

This EV falls in the range of -6 to -3. It would probably produce the correct exposure for Aurora / Northern Lights Photography.

Absolute Exposure Value Chart

EV for specific f-stop and shutter speed can also be found on the chart below, modeled by the equations above. Don’t worry about the green lines. They are not needed.

Attribution: Wikipedia

Settings Light Value

Absolute Exposure Value assumes ISO100 only.

Since we often use ISO settings above or below 100, the camera needs a way to factor this into the equation.

The total value produced from the combination of shutter speed, f-stop, and ISO, is calculated by your camera automatically. 

We will call this camera calculated value, Settings Light Value (Settings LV).

  • Settings Light Value combines ISO with Absolute Exposure Value, making it easy to determine the correct settings for any scene luminance & shooting situation.
  • The smaller the Settings Light Value the less scene luminance is required to produce the optimal exposure. Reference the Common Light Values for Landscapes section above.

For ISO 100 and greater, 

Settings Light Value = EV – log2 (ISO / 100)

For ISO less than 100,

Settings Light Value = EV + log2 (ISO / 100)

Technical Note: At ISO 100, log2(100/100) =0, thus at ISO100, Settings LV = EV. This is why ISO 100 does not have an effect on the Absolute Exposure Value. 

Let’s look at some examples of varying camera settings and the Settings Light Value they produce.

Shooting Examples – Settings Light Value

The following examples compare different settings & images, A, B, C, D, using the techniques taught above.

Settings A: f/5.6, 2 seconds, ISO100

Settings Light Value A = Log2((5.6^2)/2) –  log2 (100/100) = 4.

Referencing the Common Scene Light Values for Landscapesabove, 4 falls into the darker part of twilight.

The image produced is shown below, photographed in the Mount Baker Wilderness of Washington State.

The next image was taken seconds after the one above, with different settings.

Settings B: f/8, 1 s. ISO800.

Settings Light Value B = Log2((8^2)/1) –  log2 (800/100) = 3.

The difference between the Settings LV A and Settings LV B is 1 exposure stop (4-3=1).

Since B is smaller than A by 1 exposure stop, the settings from B can produce an image that is 1 exposure stop brighter than A, for fixed scene luminance.

The smaller the Settings LV the more “light capturing” potential these settings contain.

Referencing the Exposure Triangle Chart and settings above, the following logical progression is performed.

Moving from Settings A to Settings B:

  • f/5.6 to f/8 is 1 stop down.
  • 2 seconds to 1 second is 1 stop down.
  • ISO100 to ISO800 is 3 stops up.

1 stop down, plus 1 stop down, plus 3 stops up, is a 1 stop up increase from A to B, in turn producing a final image B, that is 1 exposure stop brighter than image A.

Let’s look at 2 more examples…

Settings C: f/2.8, 15s, ISO1600

Settings Light Value C = Log2((2.8^2)/15) –  log2 (1600/100) = -5.

Referencing the Common Scene Light Values for Landscapes above, the Milky Way is rated at -7 to -11, which means our current settings will probably produce an image that is slightly underexposed, by 2 to 6 stops.

The following image is produced, the reflection of the Milky Way in an alpine lake. Photographed in Oregon’s Cascade Range. It’s slightly underexposed.

The next image was taken seconds after the one above, with different settings.

The settings were changed to fall within the Scene Light Value range for Milky Way Photography,  -7 to -11.

Settings D: f/2.8, 30 s. ISO3200.

Settings Light Value D = Log2((2.8^2)/30) –  log2 (3200/100) = -7.

This is the correct exposure of the scene which also falls within the Scene Light Value range for Milky Way Photography.

The difference between the Settings LV C and Settings LV D is 2, from -5 to -7.

Since Settings LV D is smaller than C by 2 exposure stops, the settings from D can produce an image that is 2 exposure stops brighter than C, for a fixed scene luminance.

The smaller the Settings Light Value, the more potential the settings have to create a brighter exposure for a fixed scene luminance.

Referencing the Exposure Triangle Chart and settings above, the following logical progression is performed.

Moving From Settings C to Settings D:

  • f/2.8 to f/2.8 is a 0 stop change.
  • 15 seconds to 30seconds is 1 stop up.
  • ISO1600 to ISO3200 is 1 stop up.

A 0 stop change, plus 1 stop up, plus 1 stop up, is a 2 stop increase from C to D. That tells us that image D is 2 exposure stops brighter than image C.

Now, let’s see how this actually applies while taking photos.

For more details visit : https://www.davemorrowphotography.com/exposure-triangle
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