The Exposure Triangle: A Guide to Aperture, Shutter Speed, and ISO | PDF

Week 2/Lesson 3 1 ……………………………………………………………………………………………………… Let’s Do Some Math Please don’t tune me out because the word ‘math’ is in the title of this section. (One hundred extra credit points for anyone who doesn’t tune me out.) Let’s pretend you’re working on a math problem and need to come up...

Week 2/Lesson 3 1 ……………………………………………………………………………………………………… Let’s Do Some Math Please don’t tune me out because the word ‘math’ is in the title of this section. (One hundred extra credit points for anyone who doesn’t tune me out.) Let’s pretend you’re working on a math problem and need to come up with three variables that when added together, equal ten. You might write an equation that looks like this: 3+2+5=10 But what if I changed the three to a one? Well, I’d have to change one or both of the other variables in order to continue having an equation that equaled ten. So instead, I could use: 1+4+5=10 or 1+2+7=10 or 1+3+6=10 or 1+9+0=10 or 1+7+2=10 or 1+1+8=10 or 1+6+3=10 We could create a whole bunch of equations using three variables that equal ten, right? We’d just have to remember that anytime we changed one of those three variables, we’d have to change one or both of the remaining variables in order to have an equation that continued to equal ten, right? We know this because we understand that each of those variables are not working on their own to create a sum of ten but are actually working together to create a sum of ten. Because those variables are interdependent, right? Ok, hold onto that thought… ……………………………………………………………………………………………………… The Light Proof Box Without light, you cannot create a photo, therefore the whole concept behind photography is using light to create a photograph. week 2/fig. 3.2 Week 2/Lesson 3 2 Think of your camera as a light proof box. The only way light can enter your camera is through an opening inside the lens, called the aperture, as shown in the photo on the right in fig. 3.2. This aperture can open very wide to let in a great deal of light or it can open only slightly, letting in a smaller amount of light depending upon the kind of lens you have. When the shutter button is pressed to take a picture, the aperture allows light to enter the camera for a set amount of time. This set amount of time is called the shutter speed. Set a slow/long shutter speed and more light goes inside the camera. Set a fast/short shutter speed and less light goes inside the camera. Once the set amount of time is up however, your camera once again becomes a light proof box. The light that enters the camera through the aperture hits something called an image sensor and creates a photograph. You can determine how sensitive the image sensor is to the light that hits it by adjusting your ISO. Increase your ISO and the image sensor becomes more sensitive to light. Decrease the ISO and the image sensor becomes less sensitive to light. It is important to know however, that only a certain amount of light is needed to create a photograph. Get too much light and your photo will be too light (overexposed). Get too little light and your photo will be too dark (underexposed). Get the correct amount of light and you have what is considered a properly exposed photograph. So, as you can imagine, it is important to know how wide to open the aperture because the wider it is opened, the more light it allows inside the camera. It is also important to know how long to set your shutter speed because the longer the shutter is open, the more light enters the camera. And it’s important to know what to set your ISO to because the higher you set it, the more sensitive your image sensor is to light. Therefore, there are three variables (just like in our math equation earlier) that can be adjusted in order to let the correct amount of light inside your camera, resulting in a properly exposed photo: 1. Aperture (how wide or how narrow the opening inside your lens is) 2. Shutter speed (how long light is allowed to enter the camera) 3. ISO (how sensitive your image sensor is to the light that is hitting it) Knowing all that, you could create the following equation: aperture + shutter speed + ISO = a properly exposed photo Just like our earlier math equation, anytime you change one of the variables, you have to change one or both of the other variables in order to get the same sum. Because of that, you can imagine that if I changed my aperture, I would have to change my shutter speed and/or my ISO in order to continue creating a properly exposed photo. However, if I changed my shutter speed, I would have to change my aperture and/or my ISO in order to continue creating a properly exposed photo. And if I changed my ISO, I would have to change my aperture and/or my shutter speed in order to continue creating a properly exposed photo. It’s just like a math equation, except in this equation you’re trying to create a properly exposed photo using three variables: aperture, shutter speed and ISO. Week 2/Lesson 3 3 ……………………………………………………………………………………………………… The Exposure Triangle The Exposure Triangle is a term used in photography to describe the interrelationship between aperture, shutter speed and ISO. As you’ve seen, these three variables (aperture, shutter speed and ISO) do not work on their own, but rather, work together to create a properly exposed photo. They work interdependently and because they work interdependently, they are referred to as the ‘Exposure Triangle.’ And just so you know, the Exposure Triangle is the foundation on which just about everything photography-related is built. For the next couple of weeks, we’re going to discuss each one of the variables in the Exposure Triangle individually and in-depth. However, since these three variables work together and are interdependent, I want you to keep the concept of the Exposure Triangle in the forefront of your mind during the next few weeks while I slowly pull all this stuff together to build a foundation. And have I told you recently how glad I am that you’re here? This document and all documents, web pages, images, and other content in the Photographers’ Workshop is copyrighted and intended only for viewing and use by enrolled members of this class. Sharing of this material with any non-enrolled person or entity is strictly prohibited. Week 2/Lesson 3 4