Hi, everybody, welcome to Episode 27 of the photography explained podcast. In this episode, I again ask the question, what is the exposure triangle?

I’m your host, Rick, and each week I try to explain one photographic thing per episode to you in plain English in less than 10 minutes without the irrelevant details. My aim is to explain things in just enough detail to help us with our photography and no more.

Let’s start with what is the exposure triangle.

This is my answer.

The exposure triangle is the combination of the camera shutter speed, aperture setting and ISO. The camera’s shutter speed and the aperture setting control the amount of light that reaches the camera sensor when you take a photograph. The ISO controls the sensitivity of the camera sensor to light. When applied correctly, these settings will enable a correct exposure to be achieved.

The exposure triangle can be used creatively to take correctly exposed photos with different aperture, shutter speed, and ISO settings. The exposure triangle is also used to take photographs in challenging light conditions, and also for creative image capture.

You can listen to the episode here

Or keep on reading. Or do both. Entirely up to you!

Where I got stuck.

Now the bit I was getting stuck on was defining the exposure triangle, which looking at my notes is still wrong, but I managed to correct myself there. I’m going to come back to that.

The exposure triangle is a combination of shutter speed, aperture and ISO. I’ll say that again in English. The three elements of the exposure triangle are shutter speed, aperture setting, and ISO. The shutter speed and aperture control the amount of light that gets through to the camera sensor, and the ISO controls the sensitivity of the camera sensor to light (in theory).

Okay, that’s it, I’m sort of happy with that. I don’t mind making mistakes (as long as I notice them that is!). I’m human and I’m not reading this entirely from a script. I do have prompts in front of me and you’ll see why in a minute.

So that’s the easy bit out of the way. And this is why in previous episodes I explained aperture, shutter, and ISO individually.

The aperture scale

So let’s remind ourselves of the aperture scale. This is the aperture scale, these are full stops.

F1.4, F2, F4, F5.6, F8, F11, F16, F22.

Each step on the scale is one stop. A stop is a doubling or halving of light.

The shutter speed range is this

1 second, ½ second, ¼ second, 1/8^th second, 1/16^th second, 1/30^th second, 1/60^th second, 1/100^th second, 1/250^th second, 1/500^th second, 1/1000^th second, 1/2000^th second, 1/4000^th second, 1/8000^th second

Each step is one stop, I stop is a doubling or halving of light.

The ISO scale

100, 200, 400, 800, 1600, 3200, 6400, 12800, 25,600

Again, each step is one stop. A stop is a doubling or halving of light.

So what does this all mean?

Surely, there must be a better way because I’ve really struggled to explain this. So I’m now going to try again and then I’m going to wrap this up – I don’t want to get too deep into this one because yeah, it’s one of those, isn’t it?

If you’re using the following camera settings

• Shutter speed 1/250^th second
• Aperture f8
• ISO 200

And your camera is saying that this is the correct exposure.

What happens if you change the shutter speed?

If you change the shutter speed to 1/125^th second you are doubling the amount of time the shutter is open, doubling the amount of light reaching the sensor.

That will result in an image which is overexposed by one stop as in too bright because too much light has got in.

Now then, if we go from 1/250^th second to 1/500^th second, that’s half the time the shutter is open, which is half the light reaching the sensor, resulting in an image which is underexposed by one stop, which is dark.

What happens if you change the aperture?

Back to the original settings

• Shutter speed 1/250^th second
• Aperture f8
• ISO 200

If we change the aperture from f8 to F 5.6 we’re doubling the amount of light getting to the sensor, resulting in an image which is one stop overexposed and too light.

If we go from F8 to f 11, we are halving the amount of light meaning that the image is underexposed by one stop, and is too dark.

What happens if we change the ISO?

• Shutter speed 1/250^th second
• Aperture f8
• ISO 200

If we change the ISO from 200 to 400, we double the sensitivity of the sensor, resulting in an image which is overexposed by one stop. If we change the ISO from 200 to 100, we’re halving the sensitivity of the image sensor resulting in an image which is underexposed by one stop.

Note – we are not actually changing the sensitivity of the sensor – we are changing the brightness of the image.

Did this make sense?

Right? that’s it in a nutshell. So you change one of these things and it overexposes or underexposes the image.

Why this matters

You can change two things, you can increase the shutter speed by one stop which is halving the time the shutter is open, but if you also open up the aperture by one stop, doubling the light, you will get the same (correct) exposure.

Creative control

This is the point. You can change two of these things or all three, which means that you could use the aperture that you want to use for a photo

If you want a shallow depth of field, or a lot of depth of field pick an aperture and change the other settings to get the correct exposure.

Or if you want to use a fast shutter speed or a slow shutter speed do the same.

That’s the exposure triangle – the relationship of the three things aperture, shutter, and ISO. And I’m hoping that now you understand that if you change the shutter speed by one stop, you need to change the aperture by one stop to get the correct exposure.

Dealing with an incorrect exposure

Now it might be that the exposure that your camera is telling you about isn’t actually correct, because the camera cannot see as much as our wonderful eyes can.

You might take a photo and because of the conditions and the way the light is your camera overexposes the image. In that case, you would adjust the shutter speed or the aperture ordinarily, to reduce the exposure so you’d go the faster shutter speed or a smaller aperture to reduce the amount of light getting in to get you to a more correctly exposed shot.

This is creative photography, and this is why the exposure triangle is so important.

You don’t normally change the ISO through choice, you change the ISO through the necessity of the other settings and the lighting conditions. If it was darker and you needed a faster shutter speed you would raise (push) your ISO.

It’s well worth spending time on this and learning it properly (through practice) because everything that you do going forwards will be influenced by the exposure triangle. So I hope this has made sense.

You might want to go to my blog post for this episode on my website, The exposure triangle explained in plain English because I find these things are easier to read than to talk/ listen about.

This has been really difficult to explain properly in words, I’ve written it down and it’s fine. So yeah, check out my website. You can also ask me a question if you want to.

I’m really going out of my sequence now! So um, yeah, check out my website – I’ve got all my other episodes to date. You can read them there and also access the podcast player.

You can see the list of things I’m going to talk about and explain and get in touch and ask me if the thing that you want to explain isn’t on there. And when I get around to your question, I will give you a shout-out and if you have a website, I will give you a link to your website from mine, which is gold dust!

Next episode

What’s next? In the next Photography Explained Podcast – well I have had a change of mind. I am going to come up with some practical applications of the exposure triangle. OK? The title is being worked on right now. And here it is! Photography Explained Podcast Episode 28 – 5 Practical Applications Of The Exposure Triangle

Thank you

Okay, thank you for listening. And I hope you’ve enjoyed this episode. This was a tough one. I’m glad I got through it. I think I’m going to find something a bit lighter for the next one. But if you did enjoy it, please leave a nice review and rating wherever you get your podcasts from. And please subscribe so you don’t miss an episode.

And if you could tell one person that by my podcast I’d be really grateful.

So this episode is brought to you by the power of sheer willpower to get through this subject once and for all.

I’ve been Rick McEvoy, thanks again for listening and giving me 10 minutes of your valuable time. And I’ll see you in the next episode.

Cheers from me, Rick

OK – that was the podcast episode.

Want to know more?

Head over to the Start page on the Photography Explained Podcast website to find out more.

And here is the list of episodes published to date – you can listen to any episode straight from this page which is nice.

Let me know if there is a photography thing that you want me to explain and I will add it to my list. Just head over to the This is my list of things to explain page of this website to see what is on there already.

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And finally a little bit about me

Finally, yes this paragraph is all about me – check out my Rick McEvoy Photography website to find out more about me and my architectural, construction, real estate and travel photography work. I also write about general photography stuff, all in plain English without the irrelevant detail.

Thank you

Thanks for listening to my podcast (if you did) and reading this blog post (which I assume you have done as you are reading this).

Cheers from me Rick