You have most likely heard many times that photography is painting with light. That may seem a bit nebulous right now but as you learn to see more clearly you will begin to see how true this statement is. So if this is true, we need to understand how to control the capturing of the light that is available to us.

As you move forward in your journey to become an excellent photographer, you need to learn very well how to control your camera. While your camera may seem like it has a million settings, there are three main settings that you need to learn how to control first.

Before we get to that point let us first define clearly what we mean by the term exposure.

What is Exposure?

In its simplest form, Exposure is the amount of light that reaches the photographic plane of a camera and is captured by the camera. It does not matter if your camera is film or digital or video, the concepts are the same.
So as our light conditions change, we need to know how to control the camera to capture the right amount of light to make the image we are imagining, or to get that perfect exposure.

The Exposure Triangle

Even though most modern cameras can be very overwhelming with the sheer number of possible settings that you can change, there are only three settings that we are going to focus on here to take maximum control of the exposure. These three settings are known as the exposure triangle.
• Aperture
• Shutter Speed

Believe it or not, you can most likely do all of these settings even on your cheap phone camera.

The Exposure Triangle: Learning How to Get That Perfect Image


Aperture is the size of the hole in your lens that allows light into your camera. You can have that hole wide open to allow more light in more quickly. Or you can close this hole down to reduce the amount of light that hits the sensor plane. By adjusting this setting you end up controlling the depth of field (DOF) of the image.

What is DOF?

In optics, particularly as it relates to film and photography, depth of field (DOF) is the distance between the nearest and farthest objects in a scene that appear acceptably sharp in an image. Although a lens can precisely focus at only one distance at a time, the decrease in sharpness is gradual on each side of the focused distance, so that within the DOF, the unsharpness is imperceptible under normal viewing conditions.

The Exposure Triangle:  Learning How to Get that Perfect Image

Example Image: Large F stop (f22) has large DOF so everything is in focus and makes lights into stars

The Exposure Triangle:  Learning How to Get that Perfect Image

Example Image: Small F stop (f 1.2) has small DOF so very little is in focus

We have created an entire video on learning how to control your Aperture Setting. See video on Setting Aperture to understand how this setting affects Depth of Field.

Video: Understand Aperture Priority

Shutter Speed

Shutter Speed controls how fast or slowly the shutter of your camera opens and closes to allow light onto the photographic plane.
A fast shutter speed is great for sports type photography to stop the action.

A slow shutter speed might be used to give a water fall that milky smooth look as all the detail is out of focus because it has moved so quickly.

The Exposure Triangle:  Learning How to Get that Perfect Image

Example: Sports action shot stopping action with fast shutter speed.

In landscape photography I frequently use long exposure to get the amount of light I need at night. When I do this, the images frequently exhibit a fun side effect. The city lights in the image are turned into amazing stars.


This setting comes from a setting on older film cameras. It indicates how sensitive the film is to light. So if a photographer was going to be shooting in low light they knew they needed a film with a higher ISO value. On digital camera we can just change this setting without putting in different film into the camera.

Tip: In general shoot with the lowest possible ISO value to produce the clearest sharpest images.

Tip: As the ISO setting goes up you are apt to get more noise or graininess in the image.

This is just part of the trade-offs that we make in photography.

The Exposure Triangle:  Learning How to Get that Perfect Image

Example:  Picture of swimmer using a high ISO because of poor indoor lighting conditions.  Note the image noise. 

Garden Hose Metaphor

A great metaphor for helping us understand Exposure is the Garden Hose Metaphor.

  • The width of the hose is aperture (how fast light can flow)
  • The length of time that the hose is left on is shutter speed
  • And the pressure of the water (the speed it gets through) is ISO

Final thoughts on Exposure

Mastering the art of exposure is something that takes a lot of practice. In many ways it’s a juggling act and even the most experienced photographers experiment and tweak their settings as they go. Keep in mind that changing each element not only impacts the exposure of the image but each one also has an impact upon other aspects of it (i.e. changing aperture changes depth of field, changing ISO changes the graininess of a shot and changing shutter speed impacts how motion is captured).

The great thing about digital cameras is that they are the ideal testing bed for learning about exposure. You can take as many shots as you like at no cost and they not only allow you to shoot in Auto mode and Manual mode – but also generally have semi-automatic modes like aperture priority and shutter priority modes which allow you to make decisions about one or two elements of the triangle and let the camera handle the other elements.

Written by Wayne Moran - Visit Website