A Quick Look at the Exposure Triangle

While you may have to study for years to become a master photographer, the same is not true to take a good photograph.

If you’re planning on using photography to teach your students or children, there’s a chance you may want more creative control over the pictures you take.

Sure, a simple point and shoot camera will probably do the trick for most of your photography needs. Your camera likely has automatic presets that will figure out the settings for you.

But if you want your students to illustrate things like motion or depth of field, then there are three key elements that you should know. You will be able to achieve these affects while creating a properly exposed photograph.

What do I mean by properly exposed?

You see, photography is all about light. In fact, the definition of photography is “painting or drawing with light.” In order for there to be the proper balance of highlights (light) and shadows (dark) in a photograph, the photograph has to be exposed properly.

In order to get good exposure, you have to know the exposure triangle.

exposure triangle graphic

What is ISO?

ISO is the sensitivity of your digital camera’s sensor (where the picture is recorded) to light.

Low ISO = less sensitive (example: ISO 100)

High ISO = more sensitive (example: ISO 1600)

If you’re taking a photograph on a sunny day, you will use a low ISO (need less light). If you’re in dark room, you will use a high ISO (need more light).

Keep in mind that when you use a high ISO, your photo will be “noisy,” which means that you will be able to see the grain in the photograph.


What is aperture?

Aperture is the size of the opening, or f-stop, of the camera’s lens when you take a picture.

Small aperture (small opening): a larger f-stop on your camera (example: f22).

Large aperture (large opening): a smaller f-stop on your camera (example: f2.8).


What is shutter speed?

Shutter speed is the amount of time that the shutter stays open to allow light to enter your camera.

Fast shutter speed: 1/60th of a second and faster (can safely handhold the camera).

Slow shutter speed: 1/30th of a second and slower (you will need to use a tripod to prevent camera shake, or blur, in your photograph).


So how do ISO, aperture, and shutter speed work together to create my photograph?

A good analogy is to think about a bucket of water.

Water bucket illustration showing proper exposure


A full bucket of water = properly exposed.

Overflowing bucket = overexposed or too much light.

Half empty bucket = underexposed or not enough light (too dark).


ISO = the size of the bucket.

aperture = the size of the garden hose used to fill the bucket.

shutter speed = the amount of time the garden hose is left on to fill the bucket.


Let’s look at a couple of scenarios:

1. small bucket + large hose = less time to fill the bucket

(Low ISO + large aperture + faster shutter speed = properly exposed)

2. large bucket + small hose = more time to fill the bucket

(High ISO + small aperture + slower shutter speed = properly exposed)

Keep in mind there may be times when you want to overexpose or underexpose your photograph to achieve a desired effect. That’s okay as long as you know why you are taking a photo that is too light or too dark.

You can use manual mode (full control), aperture priority mode, or shutter speed priority mode to change the settings on your camera. Refer to the user manual for your particular camera to learn how to make the adjustments.

Do you want to photograph a beautiful flower and blur the background?

Do you want to freeze the action of a soccer player kicking a goal?

There is a great tutorial, Photography Kick-Start Guide: Adjusting Your Camera’s Settings for the Photo You Want, that explains what settings you should use to achieve the photograph you want to create.

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Also, check out the following articles by Darren Rowse for more in depth explanations of exposure:

Learning about Exposure: The Exposure Triangle

ISO Settings in Digital Photography

Introduction to Aperture in Digital Photography

Introduction to Shutter Speed in Digital Photography

Digital Photography Tips for Beginners


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