How to Master the Exposure Triangle in your Photography

The exposure triangle is made up of the three key elements: Aperture, Shutter Speed and ISO. I’ve covered Aperture and Shutter Speed already in my previous post. Today’s focus is wrapping up the final setting – ISO. I’ll also be covering how to apply the skills you’ve learnt to practical situations and getting them all working together.

The main goal of this series is to enable you to take neutrally exposed photos, while using your camera’s capabilities to achieve your own personal style.

So What is ISO and Why is it Important?

ISO is an international standard set by the International Organisation for Standardisation (ISO). This setting is responsible for changing your camera sensor’s sensitivity to light. This is represented in a numerical value typically from 100 up to 3200 depending on your camera’s model. ISO is important, as it can lighten or darken your photo. Unlike Aperture and Shutter Speed, ISO does not change anything in relation to the blur of the photo.

It’s important to keep in mind that Aperture will change the foreground and background blur of a photo. Shutter Speed will change the motion blur in a photo.

How Do I Use ISO?

ISO is represented by a range of numbers. It’s actually the easiest setting to understand, as the number directly correlates with the amount of light your sensor picks up.

The lower the number, the less light your sensor will be able to capture. On a sunny day I generally use a low ISO as there is enough light to take a well-lit photo.

The higher the number, the more light your sensor will be able to pick up. When I’m shooting in a dim environment without an external light source (e.g. flash), I need to use a higher ISO to get a neutrally exposed photo.

What Do I Need to Be Careful of With ISO?

There is one condition with ISO that can be a disadvantage. On the flip side it can be used as a creative flair in your own personal style of photography. Because ISO is not an external source of light, and is only changed digitally (changing the sensor’s sensitivity as opposed to the aperture ring letting more light in physically, or the shutter being open for longer) it means that we get something called noise or grain.

Digital grain is different from film grain. Film grain (the texture you get in old photos) is mostly colour neutral and consists of slight luminance differences.

Digital grain, which we get when we put the ISO up too high consists of both luminance and colour differences. This means we get random pops of colour typically in shadows where there shouldn’t be any. Notice in the photo below that there are slight pops of green in the shadows around some of the rocks.

Generally keeping your ISO under 800 will ensure your details stay sharp and correct. Portrait photographers will argue not to take this above 400 as a rule of thumb. I believe it is all personal preference and is learnt by doing. For astrophotography we NEED the ISO around 1600 minimum typically – so this will also depend on your situation and the environment you are shooting.

What is the Exposure Triangle?

The exposure triangle is all three settings of your camera and how the interact with each other. Using Manual Mode, typically we focus on Aperture and Shutter Speed, as they affect the style of your photograph – whether you want background/foreground blur or motion blur. We then use ISO in partnership with the second setting to balance out the light. What setting I focus on will depend on what kind of photo I am taking.

If I am taking a portrait photo, I am going to be focussing on Aperture. This is because I want to control the amount of bokeh (foreground and background blur) in my shot. So I will set my aperture to the desired number, and then use my shutter speed and ISO to balance this out.

How Do I Balance the Light in My Photos?

For this shot of my friend, I wanted a shallow depth of field (blur in the background and foreground, creating a ‘shallow’ photo). I used an aperture of F3.5 to achieve this. Because my room was very dim, I then had to put my shutter speed down to a sixth of a second (1/6s), to create a lighter image. I was careful to put my camera on a tripod however, so as not to risk adding motion blur from my hands moving. I then had my ISO at 1600. The digital noise in this photograph is minimal, however the details are a little less smooth than if I had a properly lit studio with correct lighting.

For the shot of this car, I wanted motion blur on the dirt and background to show the speed. I focussed on Shutter Speed, putting this down to a 100th of a second (1/100th). Because a shutter speed as low as this lets in a lot of light and it was the middle of the day outside, I needed to put my Aperture up to F10, to darken the image. I kept my ISO at 100, as low as it could go so as not to add any unnecessary light to my shot.

How Does This Help Me?

By using the exposure triangle, you can take control of your photos. Using Manual Mode means that you can control the light and blur within your photo without your camera falsely compensating and compromising certain elements.

A lot of this comes with practice. It will take a little while to get the feel for balancing the settings and figuring out what works best for you. This is the fun of it though!

If you’re interested in learning how to move into Astrophotography now that you’ve learnt the basics of how to use Manual mode, you can read my part one and two via the links.

Happy shooting!

FOLLOW ME ON INSTAGRAM here