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How to Understand Exposure | Learn to Use Your DSLR

Learn to use your DSLR camera and how to understand exposure with a unique twist on the exposure triangle.

Did you know photography means “writing with light?”

Your camera captures reflections of light to create a photograph. I’ll be honest, it kind of boggles my mind how it works!

I’d be lying to say I understand the science and physics of it all.

But I do know how to adjust my camera’s settings to get the types of pictures I want in a variety of settings.

It all starts with figuring out how to control how much light reaches your camera’s sensor or film. Thi is the basis to understand exposure.

Learning to Use Your DSLR Camera

We’ve been learning how to get the most from your DSLR. In case you missed any of the lessons, you can check them out here:

Lesson 1: Automatic Modes

Lesson 2: Semi-Automatic Modes

So now that we know how to use the automatic modes, it’s time to learn how to use the Manual Mode!

This introduction to exposure will begin to explore the different parts of your camera that affect exposure and how they work together!

Understand What Controls Exposure

Cameras rely on three things to take a picture:

  • ISO
  • Shutter Speed
  • Aperture.

This is often called the Exposure Triangle because there are three parts.

But I think this term is a little confusing! There’s no way to illustrate how the legs of the triangle actually interact when they’re in a triangle.

Introduction to Exposure

Good exposure is achieved by balancing those three elements.

Each part of the equation offers some creative control that affects how your final image looks. To help you while you learn I’ve created a handy dandy Cheat Sheet!

You can download your Understanding Exposure Cheat Sheet from our subscriber printable library by clicking here or on the button below to sign up.

Before we get too far, remember that there are entire books devoted to this topic! I’m going to try to simplify the information and put it in more basic terms.

If you want to learn more, I highly recommend the book Understanding Exposure by Bryan Peterson.

Now, let’s take a look at what each “side” of the exposure triangle does!

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ISO measures how sensitive your camera’s sensor is to light. 

Wait. What?

Basically the sensor is what turns the light 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 | | 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.

But, if you’re taking pictures in a dim setting (maybe indoors or at night), the sensor needs to be more sensitive. That means the ISO number will need to be higher.

Many newer cameras have sensors with even higher ISO capabilities than shown on the diagram above!

High ISO can Cause Grainy Images

Something to keep in mind when you choose which ISO to use is something called noise

Noise shows up as discolored pixels in your photograph. Some people describe noise as looking grainy.

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 | | A simple introduction to the parts of the exposure triangle. #exposuretriangle #ISO #ShutterSpeed #aperture #DSLR #exposurecheatsheet #freeprintable

I recommend using the lowest ISO possible to minimize noise or grain in your photos.

But remember: it’s always 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!


The next part of the exposure called aperture.

The aperture is the size of the opening in you camera’s lens. It controls how much light comes through your lens and into your camera’s sensor. Remember: your sensor’s sensitivity to light is its ISO.

See how these parts of exposure are working together?

The aperture is measured by something called an f-stop.

In the diagram below, you can see the range of f-stops available.

Introduction to Exposure | | 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 smaller 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.

Aperture and Depth of Field

When you use a lower f-stop (a wider aperture), you will have a more shallow depth of field.

Depth of field is basically 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. This is great in portraiture or when you’re taking close-up (macro) photos!

In the photo below, I used an aperture of 2.0 to create a blurred background (bokeh). Isn’t it pretty?! It really keeps the focus on AnnMarie and her son.

If you want all of your photo to be in focus, then choose a higher f-stop. That gives 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 | | A simple introduction to the parts of the exposure triangle. #exposuretriangle #ISO #ShutterSpeed #aperture #DSLR #exposurecheatsheet #freeprintable

IMPORTANT: 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’ll need to set your subject further away from the background.

Shutter Speed

The last part to understand exposure triangle is shutter speed. This is how fast your shutter closes.

The shutter sits in front of your camera’s sensor and opens and closes to let the light come in through the aperture (opening) 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 | | 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 shows a range of shutter speeds. Most cameras will have much slower and much faster shutter speeds available.

Just How Fast Does Your Shutter Speed Need to Be?

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.

If I’m photographing sports, I keep my shutter speed at 1/500 or higher.

A slower shutter speed lets in more light to your sensor.

A slow shutter speed, lets you create interesting effects with motion blur (writing with sparklers, moving lights, etc.).

But with a slower shutter speed, any movement of your hand (and sometimes even breathing!) can affect whether your picture is in focus.

Tripods help you to hold the camera steady with a slow shutter speed.

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 where you’re taking the photo (ISO).

Next, control how much light is getting through the by deciding the size of 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.

If you want to understand exposure, it all boils down to how much light gets to your sensor and how sensitive the sensor is.

Easy, right?

Now Try This:

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 using an automatic setting.

Then look at the information on the screen on the back of your camera. Every camera has a different way to see this information, so just check your camera’s manual.

You’ll be able to see the ISO, aperture, and shutter speed combination the camera used.

Then you can make adjustments to achieve creative control over the image by making adjustments!

Because let’s face it, sometimes the camera gets the settings wrong.

Have you ever been taking a picture where there’s something bright in the background and then the people you were photographing end up being really dark?

Learning to Use Your DSLR Camera |

Me too!

So take control of your camera with a little bit of practice and use your manual settings!

How do you make adjustments?

So you’ve taken a picture using an automatic setting. You’ve looked at the information and know what settings the camera used for ISO, aperture, and shutter speed.

Now what?!

Let me introduce you to a super cool concept: The Rule of Equivalent Exposure!

I know. It sounds super technical, right? But this is the key to putting yourself in control!

This rule basically means that if you change one of the parts that controls your exposure, you need to adjust the other part(s) the same amount.


Let’s put those exposure bars together and I’ll show you what I mean.

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

Let’s say your camera’s auto mode used the following settings: ISO: 100, Aperture: 6.3, Shutter Speed: 1/160.

You look at the picture and it looks well exposed: the correct amount of light was used.

So why change anything?

Well, let’s say you’re taking a picture of an excited new puppy who’s moving around a lot so the puppy ended up a little blurry in the picture.

The camera got the right exposure, but it didn’t use a fast enough shutter speed.

What do you do?

Adjusting the Camera Settings:

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

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

Let’s increase the shutter speed to 1/400.

Now what?

Take a look at the shutter speed bar and count how many “stops” you increased the shutter speed: Four.

To keep the exposure the same, you need to decrease four stops on the other bars to have an Equivalent Exposure!


Well, you decreased the amount of light coming into your camera with that faster shutter speed, right? So to compensate, you need to either increase the size of the aperture or make your sensor more sensitive.

Now, 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?

Another Example:

This time the information on the back of the camera shows it used the settings below:

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

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.

If you count on the bars below, that’s an increase of five stops. That means you’ll need to adjust for a total of five stops on the other two bars.

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

You check your camera’s lens and see it only goes down to an aperture of 4.0. But that’s just a change of 3 stops.

How do you get 2 more stops of light to reach your sensor?

Simply increase your ISO 2 stops to make it more sensitive to light.

So your new manual settings are ISO: 640, Aperture 4.0, Shutter Speed 1/250.

Count Your Clicks

What if you don’t have a handy dandy cheat sheet available to figure out how to make the changes?


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 as you learn to understand exposure!

You can download your Understanding Exposure Cheat Sheet from our subscriber printable library by clicking here or on the button below to sign up.

The Next Step is to Practice!

The best way to understand exposure is to practice!

Get your camera out as often as possible and practice taking pictures.

Start with your camera in an auto mode. See what your camera thinks the exposure “should” be.

Then switch to manual mode and adjust the different parts of the exposure triangle to get different effects.

If you have any questions or would like more help to better understand exposure, you can send me an email here or leave a comment below! Follow us over on Instagram and Facebook to see everything we’re up to.

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