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Do you want to understand your camera and take great photos today?

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Photography is difficult enough, right? With all of the rules, the gear and the mathematics (what now?), it can get a little too much to get your head around. That’s why we like to simplify things.

One of the areas we can better understand is the exposure triangle. This consists of the ISO, aperture and shutter speed. Bookmark this article and use it as often as you need to.

Atmospheric blurry image of people on a train - understanding the exposure triangle

Exposure Triangle

The exposure triangle helps us understand more about light. In photography, it is all mathematical behind the scenes.

Haven’t you ever wondered why the numbers seem strange, and increment in an even stranger way?

Apertures rise from f/1.4 to f/2.8 and go all the way to f/22. Shutter speeds could be 1/125, or 1/250 and all the way to 1/4000 (if you’re lucky).

Same goes for the ISO where it jumps from 100 to 200 and keeps going to 3200.

A diagram explaining the exposure triangle - iso shutter speed aperture


ISO is your camera’s sensitivity to light, with a typical range of 100-1600. Some cameras can go as low as 50 or 64, and reach as high as 12,600, but these are found in very expensive camera bodies.

Basically, the lower the ISO number, the less light is hitting your sensor.

More light is needed at the lower ranges to get a good exposure, meaning more light for the higher ranges. The lower the number, the better the resolution and quality of your resulting images.

Higher ISO numbers allow you to photograph in low light conditions, yet these settings bring more grain.

DSLRs can cope well with high ISO numbers as their sensors, processors and large pixel sizes are able to cope with the digital noise. However, as a rule, use an ISO with a value as low as possible.

For shooting in a sunny day, ISO’s 100-200 are perfect. If you head indoors, you may find that you will need to use ISO’s 800-1600.

Close up of a person changing ISO settings on a DSLR camera


The aperture is the hole inside your lens, which acts as the ‘iris’ similar to your eyes. A wide or low-number aperture, such as f.2/8 will have a very small focal length.

This means that wherever you place your focus, only a small part of the subject will appear clear.

A narrow aperture, such as f/16 will place the entire scene in focus, as it has a large focal area. Landscape photographers are more likely to use a narrow aperture if they want to show the foreground and background as clear and sharp.

The lower the f-stop, the more light is allowed to enter your lens, and therefore, hitting your sensor.

To keep my ISO value down, to retain quality, I shoot live musicians with a wide aperture. This gives me more usable light.

A high f-stop number gives me less light to play with, which tends to mean that a longer exposure is needed. To create images with a bokeh background, you would use a wide aperture.

Close up of a camera aperture - exposure triangle

Shutter Speed

Your shutter speed can be thought of as the amount of time your camera’s shutter stays open. The longer it stays open, the more light enters your scene and therefore your image.

These numbers are shown in fractions of a second, where 1/250 of a second is a typical value.

Your shutter speed has an effect on the sharpness of your subject. Lower shutter speeds let in more light, but also allow more blur from your subjects, especially if moving.

A faster shutter speed lets in less light, but gives you a sharper image as the subject is ‘frozen’.

Without a tripod, I wouldn’t recommend a setting below 1/100th of a second, unless you are taking advantage of a creative motion blur.

A shutter speed chart is another great way to remember what shutter speeds are best for each situation.

A shutter speed chart infographic to help understand the exposure triangle

Combining the Settings

Well, the numbers do have a pattern and they are chosen so. Look at aperture for example, and see if you can spot it. A typical range would be f/1.4, f/2.8, f/4, f/5.6, f/8, f/16 and f/22. The numbers almost double every time.

For the ones that don’t (f/4 and f/22), they are usually the previous two numbers added together (or thereabouts).

The same goes for ISO, where the numbers double each time. 100 goes to 200, then 400, 800, 1600 and finally 3200. Shutter speed follows suit with 1/125, 1/250, 1/500, 1/1000.

Each of these numbers is one stop. They either add or subtract one stop’s worth of light from your image. The reason we show them in a triangle is that they all work together.

For example, you have a correct lighting scene at ISO 100, shutter speed at 1/125 and an aperture of f/16. But what happens when the sun disappears behind a cloud?

The scene just got two stops darker.

This means you need to add two more stops of light into your settings for a correct exposure.

You could add it using ISO, changing it from 100 to 400 (100 -> 200 -> 400). Here, you compromise the resolution and quality of your image. A higher ISO brings grain and digital noise.

Your shutter speed could change two stops from 1/125 to 1/30 (1/125 -> 1/60 -> 1/30). In doing this,  you will have a high level of camera shake in your image. we can’t change them without compromising the image.

In this case, we would change the aperture from f/16 to f/8 (f/16 -> f/11 -> f/8).

A note from Josh, ExpertPhotography's Photographer-In-Chief:

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Craig Hull

Craig is a photographer currently based in Budapest. His favourite photographic areas are street and documentary photography. Show him a darkroom and he'll be happy there for days. As long as there are music and snacks. Find him at and Instagram/craighullphoto

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