Exposure Triangle

Photography - 101 Basic Photography Concepts
13 minutes
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At this point, you should all understand the basics of how the camera works. And we just showed you how to control each of the exposure related functions, or aperture or shutter speed and ISO. Now what we want to do in this video is give you all a real world analogy or a real demonstration on how the exposure triangle works and mainly basically, how the aperture or shutter speed and ISO work in conjunction to get to the right exposure. Now each of these things affect each other. Now what we have here is a little demonstration and we have cups labeled ISO 100 204 hundred and actually, I don't know if this is a real world analogy because I don't know who does this in the real world, but it is going to be a good visual example of each of these components and how they relate to each other.

Now before continuing, what I want to tell you all is when you think of these three components are shutter speed or aperture and your ISO. I want you to think of each of these pieces in the exposure triangle as having both an exposure related control and also an artistic related control. We're going to talk about that in this video. So let's start from the top with our shutter speed. Now, if you remember from before, if I pop this lens off of my Canon, which again, do not do this at home, I can flip the mirror up and we can see the shutter door right underneath the mirror. Now the shutter is what controls the duration, that light is going to be reaching the sensor.

So the amount of time, this can generally measured in fractions of a second, so one 500th of a second one to 100 of a second and so forth. We can even go to the other side we're measuring in whole seconds. So one second two seconds, 10 seconds, we can even go two minutes for what we refer to as shutter drags, we're trying to create really artistic, long dragged out kind of effects in these images. So the artistic related component is basically in whether we choose to freeze motion or show motion, the faster the shutter speed at higher numbers, say one 501 1,000th of a second we're going to be freezing the motion or images while the slower shutter speed on the shutter drag side we're going to be showing the motion. So that's the artistic component of shutter speed. Now let's focus on the exposure component of shutter speed.

So we have our cups here ISO 100, ISO 200 and ISO 400. We're gonna get to the ISO in just one minute we'll talk about In a second, for now, let's use the ISO 100 cup. But what I want you all to realize is that these three cups they represent the exact same desired exposure. And to get to that exposure, we need to fill the cup with light, which in this case is going to be water and we need to get up to that top line on each of these cups. Okay, so let's go ahead and grab our ISO 100 Cup, I'm going to get my phone out and we're going to just open up the faucet. So this is the amount of light that we have coming out is our water.

All right, we're going to time how long it takes to get to a proper exposure with this amount of light coming out. Alright, so we're going to go ahead and just use my phone and we're going to start the stopwatch as soon as we bring it under the water now. Now you can see that the light is coming out at a fairly slow pace right now. So it's going to affect the duration, we're gonna have a longer duration here. So to get the top we need roughly 12 seconds Okay, so I'm going to go ahead and just set this down now. So that represents our shutter speed you can see right here so to get our ISO 100 cup to our desired exposure We needed the faucet to be open for 12 seconds, that duration of time is our shutter speed.

And of course, we're going to be rounding these to the nearest whole number because well this is not a very exact way of measuring. Let's move on now and discuss the aperture and to demonstrate that I have a really cool lens I wanted to show you all on modern DSLRs we're actually controlling the after digitally through the camera itself, but this is an old film manual aperture lens, and so we're actually controlling the aperture manually with an aperture ring. The aperture is the eye or more specifically the pupil of our lens which controls the amount of light that reaches the sensor at any one point in time. Now here on my manual aperture lens, I'm set to F 3.5. This is the widest this aperture can get it's the most open, and at this point we're going to be allowing more light than if I were to stop it down.

So for example, as I go to F 5.6, the aperture shrinks up a little bit. At eight it shrinks again f 11, f 1622 and 30 to each one of these stops down reduces the amount of light and you can see that as the aperture opening closes up. Now the numbering system for the aperture is a little bit counterintuitive. After all with shutter speed and with ISO, well, we basically just double or half the number, why do we have these weird numbers with the aperture? And why is it basically getting smaller as we go higher up in the number? Well, first, you need to realize that the aperture is actually a fractional measurement.

So it's not actually f 3.5. It's one over 3.5. And it's not f4. It's one over four, and it's one over 11. And you know that when you go up in fractions, if that bottom number is larger, you're actually having a smaller number there. So f2 is a larger opening than f4, because that's one over two, which is one half and one over four, which is going to be smaller.

We'll talk about this in more detail as we keep going. But that is the exposure function of the aperture controlling the amount of light coming in at one point in time. What about the artistic component? Well, the artistic component of the aperture is in controlling the depth of field, the lower the aperture number, so as I go back down to f 3.5, we're essentially decreasing our depth of field Now what this means is that anything that's behind the area that we're focusing is going to get blurred out, or it'll fall into bokeh as we refer to. So that's that kind of pleasing background aesthetic of the blurred out area that's out of focus, as we stop down the aperture to these higher numbers, so f 22, and F 32, then we're increasing the depth of field so we get more area in our image in focus.

So that's basically the artistic side of controlling the aperture. All right, so let's get back to our faucet analogy. Now what would the aperture be in our faucet? Well, the apertures essentially that inside component that controls the amount of water coming out so as we bring the fossa handle up, that opening is larger, this would represent a large aperture, say f two or F 2.8. And this is the maximum amount of light that we can allow through the faucet. Alright, so this is our widest open aperture.

Now as I stop it down, that opening, allowing the water through is starting to close down, we're allowing less and less light through and we get down to no light. So that's our after and our faucet now let's go ahead and go back to our So 100 Cup, I'm going to dump this out. And what we're going to do is we're going to open up our aperture or open up the faucet all the way and we're going to see how that affects our shutter speed. Because the first time we did this, we didn't have the faucet open all the way. So let's go back to our little timer right here. I'm going to open this all the way, we have the max amount of light coming through.

Let's go ahead and measure the amount of time it takes. Now I'm gonna hit start, you can see it filling much faster to our desired exposure and right there. Okay. Okay, so to get to the same desired exposure with the sink open all the way. Now we only need a six second shutter duration. So it looks like we actually allowed double the amount of water in by opening the faucet up all the way this would represent one stop brighter in your aperture and we're going to talk about stops in just a second.

It's just a simple term, but just know that we doubled the amount of water coming through which allowed us to cut the shutter speed in half to six seconds. Okay, so that is our exposure component of our aperture and we now need to jump into ISO now the ISO So represents a measurement of the sensitivity of light of our sensor if we're talking about a digital camera or of our film if we're talking about film cameras, but what does that exactly mean? Well, essentially what we're saying is that if you increase the sensitivity of the sensor itself to light and that means you need less light to get to the exact same exposure, and that's what we have here. So remember when we talked about this first, we said that each of these cups represented the exact same desired exposure, that's because of ISO 100, we need this much water and this happens to be a 32 ounce cup.

So we need 32 ounces of water to get to that correct exposure or 32 ounces of light. That really doesn't make sense, but that's how much light we need. Now ISO 200, were at double the sensitivity of ISO 100. So we need half the amount of light so in this case, we would only need 16 ounces of water or 16 ounces of light to get to the same desired exposure. at ISO 400. Again, we've doubled the sensitivity from ISO 200.

So now we need half of ISO to hundreds amount of water to get to the exact same desired exposure, that is the exposure side of ISO, but what about the artistic side? Okay, so the artistic side is a little bit different when we talk about ISO because any step up that you go on ISO is going to reduce overall image quality, essentially a step up to ISO 200, or ISO 400, or ISO 800. Each step up is going to reduce overall dynamic range, it's going to reduce color, it's going to introduce grain and noise, which will kill your detail and so forth. So in general, I would say that the goal is going to be to maximize the quality of your images. And some of you might be thinking, well, if I want to achieve that filmic Look, why not go outside in the middle of the day and shoot ISO 1600 just so I have some grain and have less color, and so it looks more filmic.

Well, there's a problem with that we can actually create filmic looks in post production fairly easily. But the problem is that if you go out and you shoot at ISO 1600, the middle of the day, well, that's the way the images are going to be it's only going to be at that quality level. Regardless, you can't ever go back back and undo that. So if we shoot that way strictly for the purpose of getting that filmic look, then if we ever wanted those images, to essentially be that full quality and be full sharpness and have the best color and so forth, we wouldn't be able to go back and make that adjustment. Whereas if we always shoot at the lowest possible native or the lowest possible ISO, we can always go in and post production and we can add noise and grind to create those filmic looks that we want.

So save those types of things for post production, what I would say is as a general rule, shoot at the lowest possible ISO to get your desired exposure or to get the settings that you need in camera to get the exposure you want, and then make any other changes in post production to get those kind of filmic effects and so forth. Now, let's go back to our analogy here. What we're going to do is just open up the faucet all the way I want to demonstrate basically how these different ISO settings are going to affect our overall exposure and our shutter speed. Okay, so let's go ahead and dump this cup out. We're going to open up the aperture of our faucet, all the ways that we're allowing in the maximum amount of light, which in this case is one. Let's get our little phone here and we're going to start measuring.

Okay, so we had six seconds before, I'm going to double check to make sure that's right. So go ahead and we're going to start we should get to about six seconds to get to a proper exposure with our ISO 100. Okay, I went a little bit over whether we're at 6.7 seconds, so close enough. So we're going to say six seconds is going to be our correct shutter speed to get our ISO 100 cup full to our desired exposure. Let's check out the ISO 200 cup. So now we only need half the amount of light so we should need three seconds shutter speed start, let's see and stuff.

Look at that. I just want to show this to you. Oh, can you see that 3.06 seconds so exactly half the shutter speed of ISO 100. Okay, let's go ahead to our ISO 400. Now we need half the amount of light from ISO 200. So this should be 1.5 seconds.

So start Stop. So our final time with our ISO 400 Cup was 1.28 seconds, I probably hit the stop button a little bit too quick. For the sake of argument, we're going to say 1.5 seconds. So I'm going to go ahead and close our faucet or aperture now. Now what you saw here was that the ISO sensitivity allowed us to manipulate the shutter speed. and in this situation we're manipulating shutter speed but in other situations, you might use it to manipulate the aperture It doesn't matter.

But let's say for example, that this was a case of we're shooting say a runner or an athlete, and as we're shooting the athlete, we notice that we're at 100 per second for our shutter speed, but at 100 per second, we're not freezing the motion enough, so the runner is just a little bit too blurry. So what we need to do is double the shutter speed but let's say for example, that our aperture is fixed at F 2.8. We can't go any wider because the lens won't allow us to so this is the maximum amount of light we can get in the lens where ISO 100 and at this point, the only option we have is to increase the ISO speed to increase the sensitivity From 100 to 200, or 100 400. Of course, each of these steps up is going to reduce quality but it allows us to increase the shutter speed to get a usable image.

After all, if your shutter speeds too slow to even get something sharper to get the desired kind of compositional effect, then it doesn't matter what kind of dynamic range you have, it doesn't matter the sharpness, nothing else matters. So ISO is kind of that last resort option at least that's the way that I use it. I adjust my aperture and my shutter speed for my composition and then I'll adjust my ISO if I can't get to the correct exposure with those two adjustments by itself otherwise I leave it at ISO 100 all the time. Okay, so final recap. Our shutter speed is controlling the duration of time light is reaching a sensor. The aperture is controlling the amount of light reaching the sensor and the ISO sensitivity is controlling well the overall sensitivity or the amount of light required from the sensor to get to your desired exposure.

Now it's assignment time and what I want you all to do is practice everything, all the concepts that we've learned here in six minutes. Our triangle example, except don't do it in front of your sink, don't go get measuring cups. Instead, you already know how to adjust your shutter speed your aperture and your ISO manually on your camera. So go out in manual mode and I want you to play around with these three settings. Notice how basically adjusting your shutter speed is not only going to adjust the overall exposure but also affect whether you're capturing and showing motion or whether you're freezing motion. Notice how when you adjust your aperture you're not only adjusting exposure, but you're also adjusting the depth of field in your scene.

And then basically when you are in situations where you can't get to the right shutter speed or the right after setting and get the desired exposure will tweak your ISO sensitivity to get you there. That's it for this video and I'll see you on the next one.

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