Hi, everybody. Welcome to Episode Four of the photography explained podcast. In this episode, what is the exposure triangle?
I'm your host, Rick, and each week, I will try to explain one photographic thing 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.
Sounds good? Okay, let's do this.
So, what is the exposure triangle?
Blimey, I have to start by saying that this is going to be a tricky one. It's quite a hard thing to explain. Certainly, in words, it's easy to explain with a camera in front of somebody, but I'll give it a go.
I've got 10 minutes to explain something complicated, but hopefully I have a cunning plan for how to explain it, which was the way I got my head round it.
Is this important?
Yes, it is. This is particularly important.
So, what is the exposure triangle?
Well, there are three elements to the exposure triangle. These are
The combination of these three camera settings determines if an image has been correctly exposed or not.
What's the correct exposure then?
Well, a correct exposure is one where the balance of light is correct. That's not a very good explanation. But the way I explain a correct exposure is by explaining what an incorrect exposure is.
Don't worry, this will make sense.
In simple terms, if an image is not correctly exposed, then it's either underexposed or overexposed. What does underexposed mean?
I have to be careful here because I get these the wrong way round sometimes - this is why I've gone to plain English!
Underexposed
An underexposed image is darker than a correctly exposed image. Yes, that's right. With an underexposed image, not enough light has reached the sensor resulting in a darker image.
An underexposed image has lost highlights and lights and is incorrectly exposed.
Basically, with an underexposed image you've lost data from the right-hand end of the histogram, or as I like to call it, all the bright stuff.
(Post podcast note – I will explain histogram in another episode I promise).
So, what does overexposed mean?
Well, this is pretty much the opposite of underexposed, ok it is actually the opposite of overexposed. An overexposed image is lighter than a correctly exposed image. With an overexposed image too much light has reached the sensor resulting in an image that is too light.
And overexposed image has lost shadows and darks and is incorrectly exposed. If you look at the histogram (which I do not use that often to be honest with you) you've lost data on the left (dark) side of things
Basically, you've lost data in the darks and the shadows. And that's pretty much it. So, the correct exposure is the right balance of the highlights and the shadows, lights and darks and all the bits in between
You're not losing data at either end, well, you probably losing a little bit of data, but only a little bit. And that's the correct exposure.
Not as good as the human brain
I have to say here that when you take a single photo with a camera, it cannot record what you can see with your eyes. You will lose data at both ends. But with the correct exposure, you've recorded the maximum amount of data that you can in a single image.
That makes me think that next episode, I should talk about HDR, but I'll come back to that one, I'll get through the three parts of the expose triangle first.
I'll make a note of that one though.
This is where it can get complicated, but I'll try to keep this simple and easy to understand. Let's explain what these three parts of the exposure triangle are.
Aperture
Well, this is simply the opening in the camera lens that lets the light in when the shutter is open. The size of the aperture can be changed, letting more or less light in when the shutter opens and exposes the camera sensor to the light focused by the lens.
Shutter speed
The time the shutter is open can be adjusted to let more or less light reach the camera sensor.
ISO
The third element is ISO. This is the sensitivity of the camera sensor to light. This again can be adjusted to make the sensor more or less sensitive to light.
Putting this together
Each of these three things (on most cameras I have to caveat) can be adjusted. They can all be adjusted relative to each other. So hopefully you're with me so far.
The combination of the aperture shutter and ISO are what produced the exposure of an image. If you change one of the elements, then this changes the exposure. And to explain this I need to go to a very unfortunate term called stops.
What the are stops?
If photography was being invented today, we wouldn't have things such as stops and terms like F11 and F16.
And all these baffling things that don't seem to relate to each other.
I'd like to think that we'd have nice linear metric scales such as one to 10, which would make sense.
But for now, we'll stick with the old terms.
Aperture, shutter and ISO can be changed in units called stops (or half stops or third stops).
What is a stop?
A stop is in effect, a halving, or a doubling of the amount of light. You can check this out online if you want to know more about it. I'm just giving you examples because I haven't got much time.
Excuse the coughing.
Stops explained - aperture
With camera aperture, if you adjust the aperture from F8 to F11, this is an adjustment of one stop. The aperture has been made smaller, so it allows one stop less of light through to the aperture. That one stop is actually a halving of the amount of light.
Same with the shutter
If you change the shutter speed from 1/60th second to 1/125th second, this is also an adjustment of one stop, the shutter is open for half the time with the 1/125th setting, letting one stop less light, or half the light through to the sensor.
The same applies with ISO
ISO100 to ISO200 is an adjustment of one stop. With an ISO of 200 the camera is, or more accurately the camera sensor should I say (apologies) is twice as sensitive to light as an ISO of 100.
And what does this all mean?
If you change the aperture by one stop from F8 to F11, halving the light and change the shutter speed by one stop from one 60th of a second to 1/30th second (doubling the light) then you have the correct exposure.
And that is the exposure triangle explained
The exposure triangle allows you to take a correct exposure with any combination of ISO, shutter and aperture and then change mainly the aperture and shutter speed to get creative effects while still getting the correct exposure.
That's the fundamental point I wanted to get over here. The three are related and are completely interchangeable. You can also use the exposure triangle to deliberately change how an image is captured.
Another example
If for example, the camera said 1/60th second at F8.
If you wanted to make the image slightly darker, you could increase the shutter speed by one stop (halving the amount of light).
Or you could increase the aperture by one stop (halving the amount of light).
I always get this wrong. That's why it's such a complicated mess.
Basically, get your camera, put it in manual mode, set the dials to the correct exposure and looking through the viewfinder change the aperture and the shutter, and you'll see exactly what I'm talking about.
That'll probably be on an LCD screen these days.
Quick recap
Okay, so to recap, the exposure triangle is a relationship of the three elements aperture, shutter and ISO. different combinations of the three elements can produce correct exposures.
Yet more examples
Here are three examples of the same exposure – F8, 1/250th second, ISO 400.
If you change aperture to F5.6 and change the shutter speed to 1/500th second (without changing the ISO) it's the same exposure.
As is F5.6 and 1/250th second at ISO200.
Okay, enough examples – I could go on about this forever. I am really hoping that I have explained the exposure triangle and that you now understand it. Please let me know.
Next on the photography explained podcast
Well, let's get right into those three elements of the exposure triangle. I might start with apertures - It begins with a.
Okay, I'm done for this week
Yep, 10 minutes will be achieved. Thank you very much for listening. And I've hope you've enjoyed this episode. If you did, please leave a nice review and rating wherever you get your podcasts from. And please subscribe to so you don't miss an episode.
And you could also help me tremendously by telling anybody who you think might be interested in my musings about my podcast. And if they could listen, that would be wonderful. You can also check out my website Rick McEvoy Photography where you can find out all about me and my architectural and construction photography work, as well as my blog where you can learn lots more about my photography.
Finally, if there's something you want me to explain in my own inimitable style, please let me know. Just head over to my website. Post podcast episode note – check out the Photography Explained Podcast website. There's lots of ways you can get in touch. And with that, I will say thank you again for listening, and I'll see you on the next episode. Cheers from me, Rick.
SUMMARY KEYWORDS
exposure triangle, light, aperture, exposure, shutter, iso, photography, camera, explain, image, underexposed, darks, exposed, correct, elements, podcast, adjusted, underexposed image, shutter speed, sensor