01 June 2024

Introduction to the Photography Exposure Triangle

Learning Photography Exposure (For Application in Canon P / Av / Tv / M Modes) 

Introduction to the Exposure Triangle: ISO / Aperture / Shutter Speed
Canon EOS 70D / 300mm Lens ISO 100 f/13 1/125s

Learning Photography Exposure:  ISO / Aperture / Shutter Speed

The objective of this article is to provide new photographers (irrespective of Canon EOS / EOS R / PowerShot camera) with an introduction to the Exposure Triangle and the inter-relationship between the three fundamental exposure elements:
  • ISO
  • Aperture 
  • Shutter Speed 

Camera / Lens EXIF Data
EXIF Data is the identification and listing of an information tag and its value (available for DSLR / Compact / Smartphone cameras after taking the photo) - generally found on your LCD screen viewing image detail or when downloaded in Google Picasa / Adobe Lightroom (and other camera / editing software). Read more>>

Introduction to the Exposure Triangle
Every photo taken with a DSLR / Compact / Smartphone camera will offer / use a variety of settings to expose an image as ideally as possible to the photographer’s vision and planning.

Exposure Triangle for Achieving an 'Ideal Exposure'

Introduction to the Exposure Triangle: ISO / Aperture / Shutter Speed
Exposure Triangle Model Compiled by Vernon Chalmers Photography

Exposure Process
Exposure is a photographic process of light reflecting off a subject through the camera lens onto the camera's image sensor for a specific period of time. The relationship between ISO, Aperture and Shutter Speed settings will determine the final exposure of light (for each image) captured by the camera's image sensor - and will represent a given Exposure Value (EV).

Relationship between ISO, Aperture and Shutter speed
In understanding ISO, Aperture and Shutter Speed it’s important to note that all three are present in every photo you capture with your camera. The degree in which they are applied will depend on various camera and / or lens settings and lighting conditions. The main camera control over the inter-relationship between the three will be decided by the photographer in selecting the most appropriate shooting mode (in Auto Mode the camera will select the exposure settings, with limited other manual / photographic control).

Aperture demonstration for new photographers View

In most cameras today you will not find ISO / Aperture / Shutter Speed settings on the main mode dial of the camera, but either as separate switchgear or tucked inside the menu system – to be used with other settings (when selecting your shooting mode (Auto / P / Av / Tv / M Mode).

Auto-ISO is also an option that many new and experienced photographers are using.

Photographic Genres and the Exposure Triangle
As we developed as photographers we learn how to properly set the exposure for different genres. With Birds in Flight (action) a fast enough shutter speed will be a priority, for a distant landscape the attention / focus will be on a smaller aperture / f/stop. In long exposure / night photography we would like to keep the ISO as low as possible to minimize noise, but may opt for a 30 seconds or longer expose (ito of shutter speed). At all times all three settings of the Exposure Triangle will be configured to assist the photographer with the type of exposure required.

Camera Shooting Modes
In Automatic Mode the camera will decide the exposure settings for the photographer, in the Semi-Automatic Modes (Av / Tv) the camera will decide at least one exposure setting and in Manual Mode the photographer could take full control of all three exposure settings - many photographers who prefer Manual Mode may leave the ISO on Automatic and only set the aperture and the shutter speed.

P Mode Canon PowerShot SX40 HS f/5.6 ISO 100
P Mode: Canon PowerShot SX40 HS f/5.6 ISO 100

All DSLR cameras and the more advanced compact cameras will have at least the following shooting modes in which the ISO / Aperture / Shutter Speed exposure setting will be automatically / manually controlled by camera and / or the photographer.

Auto Mode
In Automatic Mode the camera will decide the best exposure and the photographer will have no control over any ISO / Aperture / Shutter Speed settings. Best use: when new to photography and / or uncertain about setting in changing light conditions.

Program (P) Mode
In P mode the camera will control Aperture and Shutter Speed with the photographer full control over ISO settings. Best use: when new to photography, shooting in changing conditions, but have control over ISO settings. Program (P) Mode demonstration Canon PowerShot SX40 HS

Aperture Priority (Av) Mode
In Av mode the camera will control Shutter Speed with the photographer full control over Aperture and ISO settings.

Best use: when controlling aperture settings for Depth Of Field (DOF) application in ie. macro / landscape / portraiture / street photography. seascapes / Table Mountain photography Canon EOS 6DCanon EOS 700D DSLR

Shutter Priority (Tv) Mode
In Tv mode the camera will control Aperture with the photographer in full control of Shutter Speed and ISO settings.

Best use: when controlling shutter speed for subjects in motion or to freeze motion of birds, people and other objects. Motor Sport / Action photography 
Canon EOS 70D DSLR.

Manual (M) Mode
In M mode the photographer will have full control over ISO, Aperture and Shutter Speed settings.

Best use
: when the photographer requires full manual control over all three settings in specific environments in ie. studio, changing light or other challenging conditions. Birds In Flight photography Canon EOS 7D Mark II

Introduction to the Photography Exposure Triangle

"The photography exposure triangle is a fundamental concept that explains the relationship between three critical elements in photography: aperture, shutter speed, and ISO (International Standards Organization). These three components collectively determine the exposure, brightness, and overall look of a photograph.

1. Aperture: This refers to the size of the opening in the lens when a picture is taken. It's measured in f-stops (e.g., f/2.8, f/5.6, etc.). A lower f-stop number means a larger aperture, allowing more light to reach the camera sensor. Aperture not only controls the amount of light but also affects depth of field. A wider aperture (smaller f-stop number) results in a shallower depth of field, making the background more blurred, ideal for portraits. A narrower aperture (larger f-stop number) increases depth of field, keeping more of the image in focus, commonly used in landscape photography.

2. Shutter Speed: This determines the length of time the camera's shutter remains open to let light in. Shutter speed is measured in seconds or fractions of a second (e.g., 1/1000, 1/250, 1", etc.). A faster shutter speed (1/500 or higher) freezes motion, suitable for sports or fast-moving subjects. Conversely, a slower shutter speed (1/30 or slower) allows more light and creates motion blur, ideal for artistic shots of moving objects or low-light conditions. 

3. ISO: This represents the sensor's sensitivity to light. A lower ISO number (e.g., ISO 100) means the sensor is less sensitive to light but produces finer grain in the image. Higher ISO settings (e.g., ISO 800, ISO 1600, etc.) make the sensor more light-sensitive but might introduce more digital noise or grain in the image. It's crucial to balance the ISO setting based on the available light conditions.

The exposure triangle involves a delicate balance between these three elements. Adjusting one parameter affects the others and the overall exposure of the image. For instance, if you increase the aperture size (wider opening), you may need to compensate by either increasing the shutter speed or lowering the ISO to maintain a balanced exposure.

Mastering the exposure triangle is crucial in photography as it allows photographers to achieve the desired creative effect and properly expose their images in various lighting conditions. Understanding how these settings interact enables photographers to make informed decisions to capture the perfect shot." (Source: Chat GPT 2023)

Example Image: Inter-relationship of ISO, Aperture and Shutter Speed

Image 1 : Canon EOS 7D Mark II  / 400mm lens Av Mode f/5.6

More of this Shoot  World of Birds Hout Bay Cape Town

hooting mode: Av (Aperture Priority) with the following EXIF data: 
  • ISO 640 – (Auto-ISO - controlled by Camera
  • f/5.6 - (aperture – controlled by photographer)
  • 1/90s - (shutter speed – controlled by camera)

Interpretation and interaction of these exposure EXIF data readings:

P Mode: EOS 700D / 10-18mm Lens IS0 800 f/4.5

ISO is the abbreviation for International Standards Organisation and an indicator of the sensitivity of light entering the lens onto the sensor. Its measured in values of ISO 50, 100, 200, 400, 800, 1600, 3200, 6400 and 12 800. Most cameras will also have an option for Auto-ISO. More advanced / professional digital cameras could have and ISO of up to ISO 51200+ (ie. Canon EOS 1D X). Most cameras including compact cameras will give an ISO range of 100 – 6400+ which is suitable for most lighting conditions.

ISO 100 is generally the setting used for outside / bright light photography and will be set higher as outside natural light or internal artificial light deteriorates. Not uncommon to set ISO 400 for indoor lighting and up to ISO 1600 for outside / low light photography. These various ISO settings are available for the photographer to adjust
for low light photography – even to leave the camera on Auto-ISO (for changing daylight / overcast conditions). It is recommended to experiment with ISO 400 - 1600 for after dark / night photography. When doing long exposures (slow shutter speeds) it is recommended to use ISO 100 - 400. Higher ISO demonstration Canon EOS 700D DSLR

Recommended ISO settings:

  • ISO 100 or 200 for sunny and bright daylight 
  • ISO 400 ISO for cloudy days, or indoors 
  • ISO 800 for indoors (without a flash) 
  • ISO 1600+ for very low light situations 

Disadvantages of high ISO settings:

  • More noise visible in the image the higher the ISO value
  • Higher ISO’s affects slower shutter speeds (for possible camera shake if handheld)

Thoughts on Atmospheric Conditions for Photographers
Image 2 - Av Mode: f/5.6 ISO 400 1/90s

Aperture is the size of the space in which light enters the lens / camera. It is measured in f/stops - a fractional formula used for allowing a certain amount of light in - ie. f/5.6 or f/11 which is controlled by the photographer via a variety of ways ie. manually doing it in Av or Manual mode on the camera body). In Auto or P mode (and Tv Mode) the camera will decide the aperture for you). Aperture is (also) used to control Depth Of Field DOF). DOF / close-up photography in Av mode 
Aperture values

f/1.8  f/2.8  f/4  f5.6  f/8  f/16  f/19  f/22 f/32 (This is lens 
dependent on a DSLR camera system, but in most cameras the setting will be on camera body). 

Image 2 EXIF Data: Av Mode

ISO 400 (low light)

f/5.6 (wide aperture for shallow Depth-Of-Field)

Shutter Sped 1/90 seconds

Deep vs; Shallow Depth-Of-Field (DOF) 
With a deep DOF more of the entire image will be in focus and its more likely to be used in Landscape Photography with smaller apertures of ie. f/11 – f/16. With shallow DOF certain areas of an image is deliberately out of focus and be used in a variety of genres (Wildlife / Sport / Macro / Portraits) where the photographer deliberately wants to separate the main subject from the
background - for this effect, larger apertures will be applied ie. f/1.4 - f/8 (see below image)

Lens Apertures f/2 - f/22

Introduction to the Exposure Triangle: ISO / Aperture / Shutter Speed

Aperture Demo: Canon EOS 6D / EF 85mm f/1.8 USM Lens f/1.8 - f/22  View 

Lens apertures In DSLR photography different lenses are used to create / select different levels of DOF depending on the lens aperture range, optical length of the lens and distance from subject. Different lenses / aperture settings will be applied for different type of photography genres requiring blur effects at various focal lengths ie. for close-up / macro, portraiture or wildlife photography. A DSLR camera system is not necessarily required for creating deliberate image blur, a compact camera with a wide aperture lens with some optical zoom will also work to some extent.

See Aperture / DOF Demonstration Aperture / DOF Demo

Aperture is used to control the exposure of a deep or a shallow Depth Of field (DOF) for a specific composition. A smaller f/number allows more light into the camera via the lens ie. f/2.8-f/5.6 and will create a shallow DOF for a close-up subject against a background (isolating a flower from its surroundings). See article Digital Noise vs Blur

Introduction to the Exposure Triangle: ISO / Aperture / Shutter Speed
Image 3: Canon EOS 7D Mark II  : 1/3200s Manual Mode
Shutter Speed
Shutter speed is the length of time the camera's shutter is open (and closing) allowing light onto the sensor for a given time period. Shutter speed is always measured in time. Measured in fractions of a second ie.1/125 seconds, but can extend past 30 seconds up to hours. Most digital cameras will have a default range from 1/4000 – 30 seconds. But can be faster up to 1/8000 depending on the DSLR model.

Slow shutter speed
Refer to the article ‘Long Exposures / Night Photography Setup & Tips
(Using Av mode) 
long exposure demo for specific
examples to learn more about specific shutter speeds.

Fast shutter speed
To freeze motion photographers use fast shutter speeds to ie freeze the wings
of a bird in motion. See Image 3 
for the example
in which I captured the Bird In Flight (Image 3) at a shutter speed of 1/3200 seconds using Manual Mode: f/6.3  ISO 500 (Auto- ISO).

Suggested Shutter Speeds

To Capture Motion
  • Moving water / waterfalls 4+ seconds
  • Fireworks 4+ seconds
  • Moving car at night 8+ seconds
  • Night photography 1+ seconds

To Freeze Action
  • Birds in flight 1/1000+
  • Moving water / waterfalls
    1/1000+ seconds
  • Cars / motorcycles 1/1000 seconds
  • Sporting event 1/500 –
    1/2000 seconds

Canon  EOS 700D / 100mm Lens f/11 ISO 200 1/125s

The ‘Exposure Triangle’ settings will be available before every photograph is captured. For the new photographer Auto-mode and / or semi-auto modes such as P / Av / Tv modes will provide assistance in getting the best exposure for a given shooting environment.

New photographers should be in no rush to ‘have to’ understand all exposure settings and shootings modes as soon as possible. Learning about them is important, but more important is getting comfortable with your camera, menu settings and your compositions.

Photography is a visually inspiring journey that if allowed, will not just develop camera / photographic skills or exploring different environments, but contribute to an overall mindfulness and satisfaction of great image capturing (and sharing).

Canon Camera Equipment Used (for example images)
  • Canon EOS 6D DSLR Camera body
  • Canon EOS 7D Mark II Camera body
  • Canon EOS 70D DSLR Camera body 
  • Canon EOS 700D DSLR Camera body 
  • Canon EF-S 10-18mm f/4.5-5.6 IS STM lens 
  • Canon EF-S 18-135mm f/3.5-5.6 IS STM lens 
  • Canon EF-S 55-250mm f/4-5.6 IS II lens 
  • Canon EF 50mm f/1.8 STM lens
  • Canon EF 70-300mm f/4-5.6 IS USM lens 
  • Canon EF 24-70mm f4L IS USM lens
  • Canon EF 70-300mm f/4-5.6L IS USM lens
  • Canon EF 100mm f/2.8 Macro USM lens 
  • Canon EF 400mm f/5.6L USM Telephoto / Prime lens 
  • Canon EF 100-400mm f/4.5 - 5.6L IS II USM Zoom lens
  • Canon Speedlite 430EX II external hotshoe flash 

Cape Town Shooting Locations
  • Birds in Flight: Woodbridge Island Cape Town
  • Fashion: Partners Hair Design Kenilworth Cape Town
  • Fireworks / Ferris Wheel: V&A Waterfront Cape Town
  • Flowers: Arnhem Milnerton Cape Town
  • Flowers Aurora Durbanville Cape Town
  • Motor Racing Killarney Cape Town
  • Perched Bird: Blouberg Strand Cape Town
  • Perched Bird: World of Birds Hout Bay Cape Town

All Text / Images / Partners Hair Model © Vernon Chalmers 2013 - 2017

The Theory of Photography

(Click to Enlarge)
Canon EOS 70D / EF 85mm f/1.8 USM Lens f/4 ISO 1600

Introduction to the Exposure Triangle: ISO / Aperture / Shutter Speed
Canon EOS 6D / 70-300mm Lens Av Mode: ISO 320  f/10  1/320s

Introduction to the Exposure Triangle: ISO / Aperture / Shutter Speed
Canon EOS 70D / 400mm Lens Manual Mode: ISO 320  f/6.3  1/2000s

Introduction to the Exposure Triangle: ISO / Aperture / Shutter Speed
Canon EOS 6D / 24-70mm Lens Av Mode: ISO 100  f/16  15s

Fireworks Canon EOS 700D ISO 100  f/11 8s
Fireworks Canon EOS 700D ISO 100  f/11  8s

Introduction to the Exposure Triangle: ISO / Aperture / Shutter Speed
Canon  EOS 70D / 100mm Lens f/2.8 ISO 5000 1/110s

Introduction to the Exposure Triangle: ISO / Aperture / Shutter Speed
Canon EOS 70D / EF 70-300mm f/4-5.6L IS USM Lens f/11 1/160s

Canon Long Exposure / Night Photography Setup & Tips View