Photography means “writing with light.” Your camera captures reflections of light to create a photograph. Figuring out how much light reaches your camera’s sensor or film is the basis of exposure. This introduction to exposure will begin to explore the different parts of your camera that affect exposure and how they work together.

Introduction to Exposure | www.simply2moms.com | A simple introduction to the parts of the exposure triangle. #exposuretriangle #ISO #ShutterSpeed #aperture #DSLR #exposurecheatsheet #freeprintable

Introduction to Exposure | www.simply2moms.com | A simple introduction to the parts of the exposure triangle. #exposuretriangle #ISO #ShutterSpeed #aperture #DSLR #exposurecheatsheet #freeprintable

Cameras rely on three things to take a picture: ISO, Shutter Speed, and Aperture. This is often called the Exposure Triangle because there are three components. But I think this term can be confusing! There’s no way to illustrate how the legs of the triangle actually interact when they’re in a triangle.

Introduction to Exposure

Proper exposure is achieved by balancing the three elements of the triangle: ISO, Aperture, and Shutter Speed. Each of these elements offers some creative control that affects how your final image looks. The trick is to learn which factors are most important to create the type of image you want to achieve in a particular environment.

Let’s take a look at what each side of the exposure triangle does.

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ISO

ISO is a measurement of how sensitive your camera’s sensor is to light.  Your camera’s image sensor converts the optical image (picture) from your lens into a digital image made up of pixels. You can set your ISO to a range of set levels, as shown in the diagram below.

Introduction to Exposure | www.simply2moms.com | A simple introduction to the parts of the exposure triangle. #exposuretriangle #ISO #ShutterSpeed #aperture #DSLR #exposurecheatsheet #freeprintable

If it’s really bright (e.g. outside on a sunny day), the sensor doesn’t need to be as sensitive. For bright settings, you should use a lower ISO number. On the other hand, if you are taking pictures in a dim setting, perhaps indoors or at night, the sensor needs to be more sensitive. Many newer cameras have sensors with even higher ISO capabilities than shown on the diagram above.

Something else to keep in mind when choosing which ISO to use is something called noise.  Noise is a visual distortion in an image that shows up as discolored pixels in your photograph. Depending on how much noise is there, you can often reduce the appearance of noise with digital editing software. In the image below, you can see the noise on the left side, and then how the noise was removed on the right side.

Introduction to Exposure | www.simply2moms.com | A simple introduction to the parts of the exposure triangle. #exposuretriangle #ISO #ShutterSpeed #aperture #DSLR #exposurecheatsheet #freeprintable

Generally speaking, try to use the lowest ISO possible to minimize noise or grain in your photos. But it’s better to have a picture with some noise than no picture at all, so don’t be afraid to use a higher ISO setting when necessary!

Aperture

The next part of the exposure triangle is the aperture of your camera lens. The aperture is the size of the opening that light comes through from your lens to your camera’s sensor. See how these parts of exposure are working together? This is measured by something called an f-stop. In the diagram below, you can see the range of f-stops available.

Introduction to Exposure | www.simply2moms.com | A simple introduction to the parts of the exposure triangle. #exposuretriangle #ISO #ShutterSpeed #aperture #DSLR #exposurecheatsheet #freeprintable

A wider opening (smaller f-stop number) lets in more light to your sensor. So a narrower opening lets in less light. A way to use a lower ISO to reduce noise in a darker setting is to use a lower f-stop so that more light hits your sensor.

When you use a lower f-stop or a wider aperture, you will have a more shallow depth of field. Depth of field is a way to express how much of your image is in focus. If your depth of field is shallow, then the subject you focus on will be in focus, but the background and foreground will be out of focus. In the photo below, I used an aperture of 2.0 to create a blurred background (bokeh).

If you want all of your photo to be in focus, then choose a higher f-stop. That will give you a wider depth of field. The image below was taken with an f-stop of 13 so that the mountains in the background and the desert foreground would all be in focus.

Introduction to Exposure | www.simply2moms.com | A simple introduction to the parts of the exposure triangle. #exposuretriangle #ISO #ShutterSpeed #aperture #DSLR #exposurecheatsheet #freeprintable

One thing to note: the f-stops available for your camera will depend on your lens. Not all camera lenses are created equal. Typically only more expensive lenses have the wider aperture openings of 2.8 and below. You can still create the appearance of a blurred background, but you will need to set your subject further away from the background. I’ll go into more detail about how to do this in a separate lesson.

Shutter Speed

The last part of the exposure triangle is shutter speed. This is how fast your shutter closes. The shutter sits in front of your camera’s sensor and moves to let the light come in through the aperture of the lens. If you think of your eye as a camera sensor, then your eyelid is like the shutter. So shutter speed is how fast your camera blinks. 😉

Introduction to Exposure | www.simply2moms.com | A simple introduction to the parts of the exposure triangle. #exposuretriangle #ISO #ShutterSpeed #aperture #DSLR #exposurecheatsheet #freeprintable

Shutter speed is measured in fractions of a second. The diagram above displays a range of shutter speeds. Most cameras will have much slower and much faster shutter speeds available.

A faster shutter speed lets in less light to your sensor. Fast shutter speeds will also freeze motion so moving subjects stay in focus. My rule of thumb when taking pictures of children is to keep my shutter speed at 1/250 or higher. And if I’m photographing sports, I try to keep my shutter speed at 1/500 or higher.

A slower shutter speed lets in more light to your sensor. With a slow shutter speed, you can create interesting effects with motion blur (writing with sparklers, moving lights, etc.). Keep in mind that any movement of your hand (and sometimes even breathing) can affect whether your picture is in focus with a slow shutter speed. A tripod can help you to hold the camera steady.

Putting it All Together

So there you have it. Exposure for an image starts with the sensor. You decide how sensitive the sensor needs to be based on how bright it is outside (ISO). Next, control how much light is getting through the opening (aperture) by setting your f-stop. And finally, control how much light is reaching the sensor by how fast your shutter opens and closes.

A great way to start learning how to take photos the way YOU want them is to start with your camera’s automatic modes. Take a photo. Then review the photo’s information on the screen on the back of your camera. You will be able to see what ISO, aperture and shutter speed combination the camera used. Then you can make adjustments to achieve creative control over the image by making adjustments.

Rule of Equivalent Exposure

How do you make adjustments? The Rule of Equivalent Exposure! This rule basically means that if you change one part of the exposure triangle, you need to adjust the other part(s) the same amount.

Huh?

Let’s put those exposure bars together and I’ll explain.

Introduction to Exposure | www.simply2moms.com | A simple introduction to the parts of the exposure triangle. #exposuretriangle #ISO #ShutterSpeed #aperture #DSLR #exposurecheatsheet #freeprintable

You take a photo using your camera’s auto mode and it used the following settings: ISO: 100, Aperture: 6.3, Shutter Speed: 1/160. The picture looks well exposed: the correct amount of light was used. But you are taking a picture of an excited new puppy who is moving around a lot so the puppy was blurry in the picture. What do you do?

Let’s try increasing the shutter speed so that it’s faster. That will do a better job of freezing the puppy’s motion.

Introduction to Exposure | www.simply2moms.com | A simple introduction to the parts of the exposure triangle. #exposuretriangle #ISO #ShutterSpeed #aperture #DSLR #exposurecheatsheet #freeprintable

So you increase the shutter speed to 1/400. Now what? Take a look at the shutter speed bar and count how many “stops” did you increase the shutter speed? Four. To keep the exposure the same, you need to adjust four stops on the other bars to have an Equivalent Exposure.

You decreased how much light is coming into your camera with that faster shutter speed so you need to increase the light or make your sensor more sensitive. Let’s say your camera doesn’t go lower than 100 ISO. That means the only place you can make an adjustment is the aperture. So you widen the aperture four stops to 4.0 to let in more light through the wider aperture opening.

Does that make sense?

Here’s another example:

Introduction to Exposure | www.simply2moms.com | A simple introduction to the parts of the exposure triangle. #exposuretriangle #ISO #ShutterSpeed #aperture #DSLR #exposurecheatsheet #freeprintable

You’re inside your home and there’s a decent amount of sun in the room where you’re taking your picture. But you’re taking a picture of your child so the shutter speed of 1/80 is too slow. It didn’t freeze their motion. You decide to increase your shutter speed to 1/250. That’s an increase of five stops. That means you will need to adjust five stops on the other two bars.

Your camera’s lens only goes down to an aperture of 4.0, so that’s just 3 stops of adjustment. The change to the faster shutter speed means you decreased how much light is reaching your sensor. The 3 stop adjustment to a wider aperture has increased how much light can reach your camera’s sensor. How do you get 2 more stops of light to reach your sensor? You need to increase your ISO 2 stops to make it more sensitive to light. So your new settings are ISO: 640, Aperture 4.0, Shutter Speed 1/250

Introduction to Exposure | www.simply2moms.com | A simple introduction to the parts of the exposure triangle. #exposuretriangle #ISO #ShutterSpeed #aperture #DSLR #exposurecheatsheet #freeprintable

Count Your Clicks

What if you don’t have a handy dandy cheat sheet available to figure out how to make the changes? Simple! Count your clicks.

If you decrease your aperture 3 clicks (more sensitive to light), just increase your shutter speed 3 clicks. It’s as simple as that.

I know this is a LOT of information in a short amount of time. I’ve created an Exposure Cheat Sheet that I think will help you!

You can download your understanding exposure cheat sheet from our subscriber printable library by clicking here or on the button below to sign up.

  Click Here to Access Your Free Printable!

Practice!

The best way to get a better understanding of these concepts is with practice. Get your camera out as often as possible and practice taking pictures first with an auto mode, then switch to manual mode and adjust the different parts of the exposure triangle to get different results.

Let me know how you’re doing! Do you have any questions? Feel free to email me or contact me through the comment section. 🙂

Follow the links below to review the first two lessons:

Lesson 1: Automatic Modes

Lesson 2: Semi-Automatic Modes

Introduction to Exposure | www.simply2moms.com | A simple introduction to the parts of the exposure triangle. #exposuretriangle #ISO #ShutterSpeed #aperture #DSLR #exposurecheatsheet #freeprintable

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