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Exposure Triangle featured image

Understanding the exposure triangle is a great way to quickly get yourself started into using the full manual controls of your camera.

Are you new to photography and having trouble getting your head around how your camera dials, i.e the shutter speed, aperture and ISO works?

And though you find the automatic or semi-automatic shooting modes are easier to deal with, you feel that it can sometimes very limiting.

After reading this post, you’ll understand how each of the exposure dials works, and how they affect the overall look of your image.

Exposure Triangle Definition:

The exposure triangle is a concept used to simplify and understand the relationship between the aperture, shutter speed and ISO.

Think of it as a quick and dirty version of how camera exposure works. In that article, I’ve covered its importance, how to quantify it (and therefore, better control it), and what it does in background when using the auto modes.

Anyway, these three are the main dials that can help you regulate how much light will be received by your camera’s image sensor or film. They work together to form the final exposure of your image.

Exposure Triangle Infographics

Ultimately, your setting for each of these controls will dictate how bright or dim your captured image is, as well as affect the image’s look and overall quality.

This is crucial to get proper exposure for your images.

The three sides of the exposure triangle and how they affect the image:

The exposure triangle is all about controlling the light hitting your image sensor.

While shooting, you have to constantly think about the balance of your three exposure controls. A good balance will help you attain the proper exposure for your image.

The idea is, you cannot change one setting without also changing at least one other exposure setting if you wish to maintain the same brightness level.

Otherwise, your image might turn out overexposed or underexposed.

In order for us to better balance our exposure, we have to understand how each control affects our images:

Side 1: Aperture

Aperture is that little hole in your lens where light passes through and projected into the sensor.

Exposure Triangle Side 1: Aperture. Close up look on the aperture hole in the lens.

For most lenses, these holes are represented as f/stops. If you see numbers like f/2.8, f/4, or f/16 in your camera, those are it.

On some cameras, they ditch the “F” entirely but you will not see any other strange set of numbers like those so it’s pretty easy to distinguish from other controls like the shutter speed or ISO.

A lower f-number means a wider opening and brighter image. While a higher f-number means narrower iris opening and a dimmer image. 

My dedicated post about aperture covers this control in more detail. It includes lots of other things you want to know about this topic, including why lower f-stop means a bigger aperture.

What’s more important for now, is to know that bigger aperture means brighter image and less depth of field. 

And just to briefly introduce you about depth of field, it is the amount of in-focus area of your image.

So if you have a smaller depth of field, you will have more blur area on your image. Conversely, more depth of field means that more elements in your photo will look acceptably sharp.

DoF is a whole other beast of a topic. I created a post covering this in more detail. It includes some information on how to control the DoF aside from aperture.

Side 2: Shutter Speed

Shutter Speed denotes how fast (or slow) your camera’s shutter remains open.

Shutter speed setting dial on old retro camera.

It is measured in seconds and usually represented as fractions. Examples are 1/30, 1/60, 1/120 and can sometimes all the way up to 1/8000 depending on your camera. These numbers are all measured in a fraction of a second.

But it can also remain open from 1 full second to 30 seconds for most cameras. In most cameras, a double apostrophe mark (“) denotes that it is now exposing for a full second(s) rather than just a fraction of a second.

There is also an option to use bulb mode which lets you expose your image for as long as the shutter button is pressed.

Faster shutter speed means less light is going to the image sensor. In turn, it will be dimmer. But it also means that less motion blur is recorded.

When you use slower shutter speed, your image might show some streaking or even areas that are blurred. Those streaking are the motion blur. It is pretty much the same phenomenon that happens with your eyes when you see a super fast moving object.

I created a more in-depth post about this topic. It discusses motion blurs and camera shake in more details as well as some tips when dealing with shutter speed. Go ahead and check out that article.

Side 3: ISO

As a beginner in digital photography, it is useful to think of ISO as the camera sensor’s sensitivity to light.

Though technically, that is not how it actually works, it is certainly designed to somehow copy how film works back in the days.

Exposure Triangle Side 3: ISO. Example of ISO 200 setting on camera.

Anyway, it is represented by numbers such as ISO 100, 200, 400, etc. Each time you double the numbers, you double the amount of brightness.

Keep in mind though that it works a little differently in the sense that it doesn’t actually affect the amount of accumulated light. It just lets you brighten your image by applying a higher voltage on the light you accumulated from shutter speed and aperture.

Without going too technical, using higher ISO will brighten up your image but at the expense of more image noise.

Image noise is a random pattern of white or colored pixels in your photo. On a well-exposed image, it is generally unnoticeable unless you pixel peep. But too much of these will make degrade the image quality.

You know that you exceeded the threshold if you see these in an otherwise smooth surface.

Going back, since it doesn’t increase the actual amount of light you gathered, keeping ISO low for as much as you can is a good practice.

If you ever need more light to brighten up your image, try adjusting your aperture or shutter speed first. For aesthetics or artistic reasons, you may not be able to increase the other exposure controls to increase the brightness. In cases like this, ISO is the way to go.

Getting it right in-camera will produce cleaner images than increasing the brightness in post-production.

If you’re looking for a little more technical explanation of ISO and how it works, check out this post. Though it is a little technical, we still try to keep it in a language that most new to photography will understand.

How to get proper exposure: The Lady Justice Analogy

Lady Justice is a little known analogy on how to get proper exposure. Little known because I just made it up. But it was pretty useful to me when I was starting out so I had to share it for those whose mind works like me.

Anyway, on actual shooting conditions, there is a fourth factor that you need to take into consideration… The actual available light in your scene.

I’d like to think of exposure as a balance scale with metals on both sides of the scale. The scale is always pre-populated with metals on both left and right side.

The “metal” at the left is the light already available in the scene. On the other side are 3 smaller metals. They represent the ISO, aperture and shutter speed settings at their “default” value. Or whatever settings they are currently at.

The Lady Justice Analogy in photography

First off, your settings are initially dictated by the amount of light source. For example, are you shooting in a very bright sunny day or in a very dark room?

Having less light in your scene means the metal on the left side is too heavy. You need to add metals to the right side to make it balance. In the real world, this means your image is underexposed. You will need to let more light in by adjusting any of the exposure controls.

While having too much light means your image is overexposed. Hence, you need to reduce the metals on the right side to achieve balance.

Let’s take underexposure as an example.

Metal on the left side is heavier. To make it balance, you can either add more ISO “metal” to the right side of the balance scale. Or maybe just adding aperture “metal” or a little of everything.

The point is to achieve balance and appease Lady Justice. This translates to proper exposure for your image.

Using Metaphors to grasp the concept of exposure triangle:

It is easier to understand something new if we associated them with concepts we are already familiar with, like the one I shared above.

Some may argue that this isn’t how camera exposure works. But let’s face it, being super technical doesn’t always make you take better photos. Not to mention, each person’s brain kinda works differently when understanding complicated things.

If metaphors and analogies get us started instead of complicated theories, then we should move forward with it. We may get some things wrong here and there, but that’s fine. We’re learning, and that’s a start. We can polish them along the way.

Also, things like being at the right moment, composition, color scheme, capturing emotions and even post-processing techniques are way more effective ways to create a beautiful photo.

That said, let me share some analogies to liken how the exposure triangle works:

The Bucket Analogy:

Think of the exposure triangle as collecting raindrops in a couple of buckets. Except for your camera, that would be millions and millions of buckets. Since I hate math, let’s just stick to a couple of buckets.

In this example, say we need to gather like 5 gallons of water on each bucket to get the proper exposure.

First, let’s dissect which is which for this analogy:

The Bucket Analogy
  • The amount of rainfall is pretty much out of your control. This translate to the actual light in your scene.
  • The aperture is the width of the mouth of the bucket, the bigger the width, the more raindrops it can capture.
  • Shutter speed, on the other hand, is the duration the bucket was left in the rain. The longer you leave it there, the more raindrops you can collect.
  • While ISO is how deep is the bucket you used. Is it a long and deep bucket or a small, not so deep bucket? Deeper bucket means you can put quite a lot of water before it fills up. In camera terms, that would be lower ISO.

There are plenty of ways to go about it and collect 5 gallons each.

We can use shallow buckets, with smaller bucket mouth then leave it longer in the rain.

Or use a deeper bucket with a bigger bucket width but leave it in the rain for just a short while.

And we’re not even talking the exact width measurements, bucket depth or duration the buckets are left in the rain. I feel it would make it more complicated which kinda defeats the purpose of an analogy.

The point is, we can use different combinations and still collect that same 5 gallons each.

The key here is, you do not want to collect too much or the buckets will overflow. In the real world, that will be overexposure.

You also do not want to collect it half full since we might not make it to the quota of 5 gallons each. As you guess, this scenario means you are underexposing your image.

The goal is to collect just the right amount of water for our quota of 5 gallons each. In other words, proper exposure.

The Faucet Analogy:

The faucet analogy is pretty similar to the bucket analogy but I think this one is a little more relatable.

It goes like this:

The Faucet Analogy
  • The aperture is the size of the tube. Bigger tube means more potential water will come gushing out when you open the faucet valve.
  • The valve, on the other hand, is the shutter speed. It will fill up the glass that will come gushing out from the tube depending on how long you have it opened.
  • Lastly, the glass is the ISO. The glass will fill up quickly or slowly depending on its size.

The idea is to achieve proper exposure by filling up the glass of water but not to the point that it will overflow (overexposure).

What I love about this analogy is, this is how your digital camera actually works in terms of how light is received to the sensor.

The first contact of light is with the lens(aperture). Then it passes through the shutter into your camera’s image sensor.

The amount of light that goes through the image sensor depends on how fast it opens and closes (shutter speed). Your camera’s image sensor will then process the light it received and render it accordingly depending on its ISO.

The only drawback is, it doesn’t really take into consideration the amount of light available in the actual location. Nonetheless, it is an easy way to remember how the exposure triangle works.


Understanding the concept of exposure triangle is the easiest way for beginners to learn how camera exposure works.

And while it doesn’t necessarily reflect how digital cameras actually work, it provides you the necessary knowledge to have the confidence shooting in manual mode.

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