Seven Sisters Camera Club


Learning how to control how much light is in your photo is an essential part of learning how to take good images. The exposure triangle is the combination of aperture, shutter speed, and ISO of your camera that helps you control the light in your photos.

How does the exposure triangle work?

The three components of the triangle work together to create a photograph. When you change one component it affects the others. If you increase the ISO, you will also have to change the f/stop and the shutter speed to compensate to keep your photograph exposed correctly.

Aperture is the opening in a camera lens that allows light to pass through. Adjusting the aperture changes the amount of light that hits your sensor, as well as the angle at which the light passes through the lens. The ratio of the opening versus the size of the lens is referred to as f/stop or f/number.

A wider aperture (lower f/stop) lets more light into the camera and gives you a shorter depth of field to focus on your subject, like in the example below. A smaller aperture (higher f/stop) lets less light in, but gives you greater depth of field. F/stops are on an exponential scale, not linear, so if you change your aperture from f/8 to f/4, you’ve quadrupled the amount of light passing through the lens.


Depth of field is the distance between the closest and farthest objects in a photo that appears acceptably sharp. Now your camera can only focus sharply at one point. But the transition from sharp to unsharp is gradual, and the term ‘acceptably sharp’ is a loose one! Without getting too technical, how you will be viewing the image, and at what size you will be looking at it are factors that contribute to how acceptably sharp an image is. It also depends on how good your vision is!

In the top example the photographer is using a large aperture i.e. one with a lower number such f1.4.

In the lower example the photographer is using a small aperture i.e. one with a higher number such as f16.

The use of depth of field can be very creative, isolating the subject by blurring the background.


ISO is a measure of how sensitive your camera’s sensor is to light. A higher ISO means more light being received by your sensor. For example, if you start shooting at ISO 400 and then change to 800, you’re doubling the sensor’s sensitivity to light. Shooting in low light requires a higher ISO, but it can cause more “noise” or graininess in your photos. In the example below, you can see how a photo taken with a higher ISO captures some details in darker areas, but also results in washed-out colours and a less contrasting image overall. Finding a balance is key.


However, raising your ISO has consequences. A photo taken at a high ISO will show a lot of grain, also known as noise, and might not be usable. So, brightening a photo via ISO is always a trade-off. You should only raise your ISO when you are unable to brighten the photo via shutter speed or aperture instead (for example, if using a longer shutter speed would cause your subject to be blurry).

The effect of noise can be mitigated by the use of software such as Topaz DeNoise, but that is for a later lesson.



 Shutter speed is a measurement of how long your camera shutter is open, or in the case of some digital cameras, how long the sensor is on. The longer the shutter is open, the more light that comes through your lens, and the more movement is captured in your photos.

A slow shutter speed is often used to convey motion in a photograph, like moving water, waves, or stars. It’s also an easy way to take photos in low light. Be sure you have a tripod on hand, though. Shaky hands have ruined many a photographer’s slow shutter speed photos.

Faster shutter speeds are excellent for capturing a moment in action, like a sports event, animals, or birds in flight. This reduces the amount of light hitting your sensor, though, so make sure your ISO and aperture are adjusted accordingly.

A slow shutter speed when the camera is panned in the direction the car is travelling gives the impression of movement and speed.

A faster shutter speed freezes movement creating a sharper image.

How do you master the exposure triangle?


In order to master the exposure triangle, you need to practice! Pick a subject and photograph it over and over, changing settings as you go.

Since you now have a basic understanding of what each component does, try to aim for certain effects. Shoot some running water and play around with shutter speed, or take some images at night. The more you practice the more you’ll understand how different adjustments affect your photos.

With digital photography it costs only your time you can delete your images later.

There is a huge number of video lessons on You Tube, I have picked a couple that may help you understand these basic principles.


Depth of field explained

What is ISO.

Shutter speed

Please don’t be shy we were all beginners once just ask myself or one of the other members and we can help you with this wonderful past time.