Intro to Photography: The Exposure Triangle

The first step towards professional starts with a thorough understanding of lighting and how to use your camera to capture the right amount of light. Exposure is a fancy way of saying how bright or dark a photo is, and you can use your camera settings to brighten or darken your photo. There are essentially three variables that determine the exposure of a photograph: shutter speed, aperture, and ISO (also known as the exposure triangle). In this quick guide, I will try my best to explain the essentials and show how they work together. To start off, I’ll quickly explain how your camera works.

Light comes through the lens into your camera, where two mirrors inside bounces that light into the viewfinder. If you have a mirrorless camera, the light hits the electronic sensor which shows up on your screen. When you click the shutter button the mirrors lift away, and the light then hits your camera sensor. A processor then reads that information of light and records it onto your memory card.

If you have been shooting on automatic mode, it's time to switch over to manual (marked M on your camera mode dial) and start learning how the exposure triangle works together to make an exposure! Let's start with the first variable: shutter speed.

Shutter Speed

Shutter speed is probably the easiest to understand out of the three. In your camera there is a shutter covering the sensor that is comprised of two curtains. When you take a photo, the first curtain opens up and starts the exposure onto the sensor (taking the photo), and when it is done, the second curtain closes it, ending the exposure (finishes taking the photo). The shutter speed controls how long the shutter stays open. The fundamental rule is that the shorter the shutter the less time the sensor is exposed to light, making it darker. The longer the shutter the more time the sensor is exposed to light, making it brighter.

Apart from changing exposure, shutter speed plays a large part on how blurry something is in your photograph. When the sensor is open longer, it will capture more things in motion. When the sensor is open shorter, it will only capture something quickly. This means that the longer the shutter speed, the more motion it will capture (yes, the motion from your shaky hands), and the shorter the shutter speed, the less motion it will capture.

The number associated with the shutter speed is calculated as 1/x of a second, or x seconds. For example, 1/250 is 1/250th of a second. 5” means 5 seconds. This is how long your shutter is open for, and how long the sensor will be taking in light/reading the motion.

How does this play in photography? Well, if you want motion blur in your waterfalls, you’d have to use a slow shutter speed to capture the motion. If you want to capture a horse galloping you’d need a very fast shutter speed to capture the movement. Here are some examples below.

shutter speed
In order to capture the silky smooth motion of the waterfall, I dropped my shutter speed to 3 seconds.

In order to capture the silky smooth motion of the waterfall, I dropped my shutter speed to 3 seconds.

Believe it or not, deers are quite quick. To capture this deer still, I was shooting at 1/800th of a second.

Believe it or not, deers are quite quick. To capture this deer still, I was shooting at 1/800th of a second.


Aperture is a measurement of how open and closed the lensiris is, which affects how much light hits the sensor. Essentially, the wider the aperture, the more light will be let in, simply because the opening is larger (see below). The smaller the aperture, the less light it will let in simply because the opening is smaller. We use something called “f-stops” to describe how wide or small the aperture is, and essentially the smaller the number, the larger the opening, the more light hits the sensor, and vice versa (as you can see below).


Now why would you want less light to hit the sensor? Not only is it a crucial part of balancing out exposure along with shutter speed and ISO (which we will touch on next), it is a fundamental cause of depth of field. Depth of field (DoF), in it’s simplest definition, is essentially how burry the foreground and background is.

A wide/large aperture (low f-stop) creates a shallow DoF, which blurs the background and foreground.

A small aperture (high f-stop) gives a large DoF, allowing more of a scene to be in focus (think landscapes). If you want everything to be in focus you would want your f-stop to be very high, like f/11. The greater the f-stop, the more everything will be in focus. Take a look at the two examples below:

The foreground here is pretty blurred out, which means I used a  wide  aperture, or low f-stop. This was shot at f/4.

The foreground here is pretty blurred out, which means I used a wide aperture, or low f-stop. This was shot at f/4.

Everything is tack sharp in this photo which means I used a  small  aperture, or high f-stop. This was shot at f/8.

Everything is tack sharp in this photo which means I used a small aperture, or high f-stop. This was shot at f/8.

This is very useful for composition as it helps create depth while focusing in on only the subject. I used DoF above to frame the town with the blurry leaves. There is tons more to know about aperture and depth of field that we won’t touch on in this guide, but perhaps I will write another blog post on it soon.

Fun tip: Most lenses are their sharpest around f/5.6 or f/8.


ISO is basically how sensitive your camera is to light. Increasing the ISO number means more sensitivity, and lowering the ISO number means less sensitivity (sensitivity doesn’t mean sharpness) Increased ISO result in more noise and less detail, often making a photo grainier. There is a lot to get to when it comes to ISO, but try your best to use the lowest ISO possible. ISO is the last resort when compensating for shutter speed and aperture, and often it is used during low light where you are already using the widest possible aperture and the slowest shutter speed you can. The lens cannot physically open itself any wider, and you need to have the photo sharp. Most photographers would rather have a grainy image than a blurry one.

how they work together

Now that you understand the three components that make up lighting, let’s see how they play together. Shutter speed controls motion, aperture controls depth of field, and ISO controls sensitivity. By adjusting any of the three, you are darkening/lightening up the photo, so you must use the other two to compensate for the adjustment. Let’s do a case study with my photos.


study one: aperture

I knew right away that I wanted some type of foreground in order to give a sense of depth and framing for this shot in Scotland. I first set my aperture to the lowest setting, which was f/2.8. I then set my ISO to the lowest setting (100), because I wanted the least amount of grain, and there was enough light during the day. All that was left was shutter speed.


study two: iso

This was a hard shot to get. First, I knew that being on a helicopter meant that I was moving, so I had to set my shutter speed high enough to keep things sharp. I found that 1/400 on this ride to be enough. I set my aperture to f/5.6, as I wanted the focus to be my feet, but also have the city in focus. That left ISO. This was taken right as the sun was set, so it was already quite dark. With my aperture and shutter speed already set, I had to crank my ISO to 1600 to compensate for the other two variables.


study three: shutter speed

For the waterfall to look silky smooth, I immediately knew that I had to drop my shutter speed to 1/15 or more. By slowing down the shutter speed, it would make the photo overexposed. I also knew that I didn’t want any grain in my photo so I set my ISO to the lowest (100). Lastly, I raised my aperture to f/8.0, as I did not have any need for depth of field.



You may be wondering, “Elliott, how do I know if my photo will be underexposed or overexposed?” Good question! In your camera viewfinder or screen, you will see something called a light meter which looks something like this:


Long story short that bar is a spectrum ranging from underexposed to overexposed. The camera reads what you are trying to photograph, and tells you if your settings will result in an overexposed or underexposed photo. The numbers on top are called exposure values (EV) or stops, which are essentially double/half the amount of light of the previous/next number. For example, 1 EV is half the light of 2 EV ( you could also say 2 EV is double the light of 1 EV). An EV is a combination of aperture, shutter speed, and ISO, as those things are what change the exposure value. You generally want to stay in the middle where the camera thinks it’s perfectly exposed. There are lots to learn about this such as types of metering, dynamic range, stops, and more, but for now, master the exposure triangle and make sure you understand how each component works. Knowing how to use these settings are second nature to most if not all professional photographers, and it will help you in the long run to understand what they do. I will try my best to write a blog post or even film a vlog in depth for each variable and on more photography related topics soon!

*Cover photo taken by Conor Luddy via. Unsplash.


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